accel/ivpu: Annotate struct ivpu_job with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct ivpu_job.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Cc: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Cc: Oded Gabbay <ogabbay@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Tom Rix <trix@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: llvm@lists.linux.dev
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Link: https://lore.kernel.org/r/20230922175416.work.272-kees@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

Author: kees

drivers/accel/ivpu/ivpu_job.h

@@ -51,7 +51,7 @@ struct ivpu_job {
 	u32 job_id;
 	u32 engine_idx;
 	size_t bo_count;
-	struct ivpu_bo *bos[];
+	struct ivpu_bo *bos[] __counted_by(bo_count);
 };
 
 int ivpu_submit_ioctl(struct drm_device *dev, void *data, struct drm_file *file);