snsc: restore IRQs on error path in scdrv_write()

This bug is as old as git.  We need to be calling spin_unlock_irqrestore()
instead of regular spin_unlock() here.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>