Resume from RAM on HPC nx6325 broken

generic_ide_resume() should check if dev->driver is not NULL before applying
to_ide_driver() to it.  Fix that.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>