drm/msm/gpu: Don't map command buffers with nr_relocs equal to 0

If a command buffer doesn't have any relocs assigned to it there then
is no need to map it in the kernel address space.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>

drivers/gpu/drm/msm/msm_gem_submit.c

@@ -317,6 +317,9 @@ static int submit_reloc(struct msm_gem_submit *submit, struct msm_gem_object *ob
 	uint32_t *ptr;
 	int ret = 0;
 
+	if (!nr_relocs)
+		return 0;
+
 	if (offset % 4) {
 		DRM_ERROR("non-aligned cmdstream buffer: %u\n", offset);
 		return -EINVAL;