drm/amdgpu: Fix no-procfs build

Fixes undefined symbol when PROC_FS is not enabled.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202305251510.U0R2as7k-lkp@intel.com/
Fixes: 376c25f8

 ("drm/amdgpu: Switch to fdinfo helper")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by:  <alexander.deucher@amd.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230525155227.560094-1-robdclark@gmail.com