drm/radeon: rename fence_wait_last to fence_wait_empty

As discussed with Michel that name better
describes the behavior of this function.

Signed-off-by: Christian König <deathsimple@vodafone.de>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index dedb398..89be94b 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -915,7 +915,7 @@
 	radeon_bo_evict_vram(rdev);
 	/* wait for gpu to finish processing current batch */
 	for (i = 0; i < RADEON_NUM_RINGS; i++)
-		radeon_fence_wait_last(rdev, i);
+		radeon_fence_wait_empty(rdev, i);
 
 	radeon_save_bios_scratch_regs(rdev);