fix(relibc): bump workspace redox_syscall to 0.8.1 too

The P0-redox-ioctl-syscall-0.8.1.patch only bumped the redox-ioctl
sub-crate's pin. The relibc main workspace still pinned
redox_syscall = 0.7.4, causing relibc itself to fail to compile
with redox-rt errors when the path-override in base pulled in
the now-0.8.1 redox-ioctl.

Bump the relibc workspace's redox_syscall to 0.8.1 to match.

local/patches/relibc/P0-relibc-syscall-0.8.1.patch

@@ -0,0 +1,10 @@
+--- a/Cargo.toml
++++ b/Cargo.toml
+@@ -68,7 +68,7 @@ plain = "0.2"
+ redox-path = "0.3"
+ redox_protocols = { package = "libredox", version = "0.1.16", default-features = false, features = ["protocol"] }
+-redox_syscall = "0.7.4"
++redox_syscall = "0.8.1"
+ 
+ [build-dependencies]
+ cc = "1"

recipes/core/relibc/recipe.toml

@@ -2,6 +2,8 @@
 git = "https://gitlab.redox-os.org/redox-os/relibc.git"
 rev = "861bbb0"
 patches = [
+    # Bump relibc workspace redox_syscall pin to 0.8.1 (matches rest of build)
+    "P0-relibc-syscall-0.8.1.patch",
     # Bump redox-ioctl's redox_syscall pin to 0.8.1 (matches rest of build)
     "P3-eventfd-mod.patch",
     # Add pub mod bits_eventfd to header/mod.rs