staging: fsl-mc: get rid of mutex_locked variables

Remove mutex_locked variables which are used to determine whether mutex is
locked, instead add another label to unlock mutex on premature exits due to
an error.

This patch also addresses the folowing warnings reported by coccinelle:

drivers/staging/fsl-mc/bus/mc-allocator.c:237:1-7: preceding lock on line 204
drivers/staging/fsl-mc/bus/mc-allocator.c:89:1-7: preceding lock on line 57
drivers/staging/fsl-mc/bus/mc-allocator.c:157:1-7: preceding lock on line 124

Signed-off-by: Cihangir Akturk <cakturk@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>