drm/vc4: Return -EINVAL on the overflow checks failing.

By failing to set the errno, we'd continue on to trying to set up the
RCL, and then oops on trying to dereference the tile_bo that binning
validation should have set up.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Fixes: d5b1a78a77 ("drm/vc4: Add support for drawing 3D frames.")

drivers/gpu/drm/vc4/vc4_gem.c

@@ -601,6 +601,7 @@ vc4_get_bcl(struct drm_device *dev, struct vc4_exec_info *exec)
 					  sizeof(struct vc4_shader_state)) ||
 	    temp_size < exec_size) {
 		DRM_ERROR("overflow in exec arguments\n");
+		ret = -EINVAL;
 		goto fail;
 	}