Fix build system: full commit hash, git clean, remove absent USB BINS from base-initfs

- Use full 40-char commit hash in base recipe.toml so the cookbook's
  caching logic correctly recognizes already-fetched sources (short
  hashes always missed the cache, causing patches to re-apply on top
  of already-patched source).
- Add git clean -fd before git reset --hard in fetch.rs so untracked
  files from previous patch applications are removed before re-patching.
- Remove ehcid/ohcid/uhcid from base-initfs BINS list (same fix as
  base recipe, these drivers don't exist in the current upstream).

With these fixes, redbear-live-mini builds and boots to login prompt in QEMU.

recipes/core/base/recipe.toml

@@ -1,6 +1,6 @@
 [source]
 git = "https://gitlab.redox-os.org/redox-os/base.git"
-rev = "463f76b9"
+rev = "463f76b9608a896e6f6c9f63457f57f6409873c7"
 patches = ["redox.patch", "P2-boot-runtime-fixes.patch", "P2-acpi-i2c-resources.patch"]
 
 [build]