base: re-sync ACPI userspace with upstream master

Phase B of the ACPI fork-sync plan (local/docs/ACPI-FORK-SYNC-STRATEGY-2026-06-30.md).
Pairs with the kernel fork-sync commit 4f2a043.

Restores the base fork to match upstream Redox OS base master for the
ACPI userspace:

- Cargo.toml (workspace):
  * Add acpi = { git = "...redox-os/acpi.git", branch = "redox-6.x" }
    workspace dependency. The jackpot51/acpi GitHub fork was
    deprecated in favor of the gitlab.redox-os.org fork that
    tracks the redox-6.x branch (has AcpiVerb-style AML updates,
    PIIX4 fixes, VirtualBox boot fix per upstream MR #243).
  * Switch redox_syscall from crates.io 0.8.1 to a git ref of
    gitlab.redox-os.org/redox-os/syscall.git, with [patch.crates-io]
    redirecting crates.io consumers to the gitlab fork. The
    crates.io 0.8.1 release predates AcpiVerb (commit 79cb6d9)
    that the kernel MR #613 / base MR #275 introduce.

- drivers/acpid/Cargo.toml: acpi.workspace = true.

- drivers/amlserde/Cargo.toml: acpi.workspace = true.

- drivers/hwd/Cargo.toml: add redox_syscall.workspace = true
  dependency. HWD now needs the AcpiVerb enum to construct Fd-based
  calls into the kernel ACPI scheme.

- drivers/amlserde/src/lib.rs: split AmlSerdeReferenceKind::LocalOrArg
  into 4 separate variants matching the new gitlab acpi crate
  ReferenceKind enum:
    Local, Arg, Index, Named
  Required by upstream commit "Update ACPI crate" (f2f834d4).

- drivers/acpid/src/main.rs: rewrite the RXSDT and kstop acquisition
  to use the new Fd::open + call_ro(AcpiVerb::*) interface:
    kernel_acpi_handle = Fd::open("/scheme/kernel.acpi", O_CLOEXEC, 0)
    rxsdt = kernel_acpi_handle.call_ro(buf, READ, &[ReadRxsdt])
    shutdown_pipe = kernel_acpi_handle.openat("kstop", O_CLOEXEC, 0)
  Also fixes the nsmgr deadlock by moving setrens(0, 0) BEFORE
  daemon.ready() (upstream commit 9dd6901d).

- drivers/hwd/src/backend/acpi.rs: rewrite AcpiBackend::new() to use
  the new Fd::open + call_ro(AcpiVerb::ReadRxsdt) interface, matching
  the kernel ACPI scheme rewrite.

Verified by: CI=1 ./local/scripts/build-redbear.sh redbear-mini
succeeded with exit 0, producing build/x86_64/redbear-mini.iso
(512 MB) at 2026-06-30 04:54.

Cargo.toml

@@ -90,6 +90,7 @@ exclude = ["bootstrap"]
 # Low-level Redox OS crates should be kept in sync using workspace dependencies
 # Remember to also update bootstrap dependencies, those are not in the workspace
 [workspace.dependencies]
+acpi = { git = "https://gitlab.redox-os.org/redox-os/acpi.git", branch = "redox-6.x" }
 anyhow = "1"
 bitflags = "2"
 clap = "4"
@@ -110,7 +111,7 @@ redox-ioctl = { git = "https://gitlab.redox-os.org/redox-os/relibc.git" }
 redox-log = { git = "https://gitlab.redox-os.org/redox-os/redox-log.git" }
 redox-rt = { git = "https://gitlab.redox-os.org/redox-os/relibc.git", default-features = false }
 redox-scheme = "0.11.0"
-redox_syscall = { version = "0.8.1", features = ["std"] }
+redox_syscall = { git = "https://gitlab.redox-os.org/redox-os/syscall.git", features = ["std"] }
 redox_termios = "0.1.3"
 ron = "0.8.1"
 serde = { version = "1", features = ["derive"] }
@@ -129,5 +130,8 @@ missing_docs = "allow" #TODO: set to deny when all public functions are document
 missing_safety_doc = "warn" #TODO: set to deny when all safety documentation is completed
 precedence = "deny"
 
+[patch.crates-io]
+redox_syscall = { git = "https://gitlab.redox-os.org/redox-os/syscall.git" }
+
 [patch."https://gitlab.redox-os.org/redox-os/relibc.git"]
 #redox-ioctl = { path = "../../relibc/source/redox-ioctl" }