drm/amdgpu: do not call insert_nop fn for zero count

Do not make a function call for zero size NOP as it
does not add anything in the ring and is unnecessary
function call.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -145,6 +145,8 @@ void amdgpu_ring_commit(struct amdgpu_ring *ring)
 	count = ring->funcs->align_mask + 1 -
 		(ring->wptr & ring->funcs->align_mask);
 	count %= ring->funcs->align_mask + 1;
+
+	if (count != 0)
 		ring->funcs->insert_nop(ring, count);
 
 	mb();