mn10300: Allow to pass array name to get_user()

This fixes the following compile error:

CC block/scsi_ioctl.o
block/scsi_ioctl.c: In function 'sg_scsi_ioctl':
block/scsi_ioctl.c:449: error: invalid initializer

Signed-off-by: David Howells <dhowells@redhat.com>