drm/msm: use %z format modifier for printing size_t

The return type of ARRAY_SIZE() is size_t, so we have to use
%zu instead of %lu to avoid this warning:

drivers/gpu/drm/msm/msm_gpu.c: In function 'msm_gpu_init':
drivers/gpu/drm/msm/msm_gpu.c:742:31: error: format '%lu' expects argument of type 'long unsigned int', but argument 7 has type 'unsigned int' [-Werror=format=]

The warning it otherwise harmless as size_t is always the
same size as unsigned long in all supported architectures,
but gcc doesn't know that.

Fixes: c2fceabca6d5 ("drm/msm: Support multiple ringbuffers")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_gpu.c

@@ -777,7 +777,7 @@ int msm_gpu_init(struct drm_device *drm, struct platform_device *pdev,
 	}
 
 	if (nr_rings > ARRAY_SIZE(gpu->rb)) {
-		DRM_DEV_INFO_ONCE(drm->dev, "Only creating %lu ringbuffers\n",
+		DRM_DEV_INFO_ONCE(drm->dev, "Only creating %zu ringbuffers\n",
 			ARRAY_SIZE(gpu->rb));
 		nr_rings = ARRAY_SIZE(gpu->rb);
 	}