staging: fsl-mc: simplify couple of deallocations

Simplify a couple of deallocations code paths. This also fixes these
checkpatch.pl false positives:
 "WARNING: kfree(NULL) is safe and this check is probably not required"

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>