drm/amdkfd: kfd_dev_is_large_bar() can be static

Fixes: 5ec7e028 ("drm/amdkfd: Add ioctls for GPUVM memory management")
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>