staging: android: sync: fix up a sparse warning

Fix up a sparse warning about sync_dump that was reported.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Cc: Erik Gilling <konkers@android.com>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>