Revert "staging: fsl-mc: delete prototype of unimplemented function"

This reverts commit be6faff7.

The whole series is broken, so back it all out.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Cc: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>