vmwgfx: return an -EFAULT if copy_to_user() fails

copy_to_user() returns the number of bytes remaining to be copied, but
we want to return a negative error code here.  I fixed a couple of these
last year, but I missed this one.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c

@@ -110,6 +110,8 @@ int vmw_get_cap_3d_ioctl(struct drm_device *dev, void *data,
 	memcpy_fromio(bounce, &fifo_mem[SVGA_FIFO_3D_CAPS], size);
 
 	ret = copy_to_user(buffer, bounce, size);
+	if (ret)
+		ret = -EFAULT;
 	vfree(bounce);
 
 	if (unlikely(ret != 0))