usb: gadget: mass_storage: optional SCSI WRITE FUA bit

The nofua parameter (optionally ignore SCSI WRITE FUA) was added
to the File Storage Gadget some time ago.  This patch adds the
same functionality to the Mass Storage Function.

Signed-off-by: Michal Nazarewicz <m.nazarewicz@samsung.com>
Cc: Andy Shevchenko <ext-andriy.shevchenko@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>