Restore DEBUG_FS=y for development/bench phase

DEBUG_FS provides instrumentation needed by TODO items 1 and 6:
- /sys/kernel/debug/dri/*/name — GPU performance counters
- /sys/kernel/debug/cma/* — per-region CMA page accounting
- /sys/kernel/debug/block/* — I/O scheduler stats (BLK_DEBUG_FS)
- Detailed thermal zone introspection

Trade-off acknowledged: small runtime overhead from debugfs mount,
but the instrumentation granularity is essential while we're actively
benchmarking and tuning. Switch to DEBUG_FS=n or DISALLOW_MOUNT
for release-final builds once FASE 1-2 benchmarks are complete.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

projects/ArchR/devices/RK3326/linux/linux.aarch64.conf

@@ -784,7 +784,7 @@ CONFIG_BLK_DEV_WRITE_MOUNTED=y
 # CONFIG_BLK_CGROUP_IOPRIO is not set
 CONFIG_BLK_CGROUP_RWSTAT=y
 CONFIG_BLK_ICQ=y
-# CONFIG_BLK_DEBUG_FS is not set
+CONFIG_BLK_DEBUG_FS=y
 # CONFIG_BLK_SED_OPAL is not set
 # CONFIG_BLK_INLINE_ENCRYPTION is not set
 
@@ -6731,7 +6731,10 @@ CONFIG_FRAME_POINTER=y
 # Generic Kernel Debugging Instruments
 #
 # CONFIG_MAGIC_SYSRQ is not set
-# CONFIG_DEBUG_FS is not set
+CONFIG_DEBUG_FS=y
+CONFIG_DEBUG_FS_ALLOW_ALL=y
+# CONFIG_DEBUG_FS_DISALLOW_MOUNT is not set
+# CONFIG_DEBUG_FS_ALLOW_NONE is not set
 CONFIG_HAVE_ARCH_KGDB=y
 # CONFIG_KGDB is not set
 CONFIG_ARCH_HAS_UBSAN=y