mmc: cb710 core: Add missing spin_lock_init for irq_lock of struct cb710_chip

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>