i915: signedness bug in check_overlay_src()

"depth" should be signed in case packed_depth_bytes() returns -EINVAL.

This probably doesn't make a difference at runtime.  In the original
code we would return -EINVAL later if (rec->offset_Y % 4294967274) is
non-zero.
Signed-off-by: NDan Carpenter <error27@gmail.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_overlay.c

@@ -946,7 +946,9 @@ static int check_overlay_src(struct drm_device *dev,
 {
 	int uv_hscale = uv_hsubsampling(rec->flags);
 	int uv_vscale = uv_vsubsampling(rec->flags);
-	u32 stride_mask, depth, tmp;
+	u32 stride_mask;
+	int depth;
+	u32 tmp;
 
 	/* check src dimensions */
 	if (IS_845G(dev) || IS_I830(dev)) {