ci: bump toolchain to v3.0.1 for fresh pocl kernel-lib bitcode

The v3.0 prebuilt pocl shipped a stale kernel-library bitcode that still
emitted a retired CUSTOM1/funct3=6/sub_op=1 window-write instruction the
Vortex decoder aborts on, breaking the OpenCL FF-TEX image tests
(image_ff, image_ff_linear, image_ff_bgra, image_hwsw). v3.0.1 refreshes
that bitcode (regenerated from current pocl HEAD); nothing else in the
toolchain changes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: tinebp

VERSION

@@ -1,3 +1,3 @@
 VORTEX_VERSION=3.0
-TOOLCHAIN_REV=v3.0
+TOOLCHAIN_REV=v3.0.1
 GEM5_REV=v25.0.0.1