drm/amdgpu/discovery: Annotate struct ip_hw_instance 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 ip_hw_instance.

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

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230922173216.3823169-2-keescook@chromium.org

drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c

@@ -654,7 +654,7 @@ struct ip_hw_instance {
 	u8  harvest;
 
 	int num_base_addresses;
-	u32 base_addr[];
+	u32 base_addr[] __counted_by(num_base_addresses);
 };
 
 struct ip_hw_id {