USB: mos7720: use GFP_ATOMIC under spinlock

The write_parport_reg_nonblock() function shouldn't sleep because it's
called with spinlocks held.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable@vger.kernel.org
Acked-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>