drm/amdkfd: Fix prototype warning for get_process_num_bos

Fix the warning: no previous prototype for 'get_process_num_bos'
[-Wmissing-prototypes]

Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_chardev.c

@@ -1648,7 +1648,7 @@ static int criu_checkpoint_devices(struct kfd_process *p,
 	return ret;
 }
 
-uint32_t get_process_num_bos(struct kfd_process *p)
+static uint32_t get_process_num_bos(struct kfd_process *p)
 {
 	uint32_t num_of_bos = 0;
 	int i;