Detect `ataraid' devices on GNU/kFreeBSD. Fix for ATA devices using
`ata' driver on kernel of FreeBSD 9.
* util/deviceiter.c [__FreeBSD_kernel__] (get_ada_disk_name)
(get_ataraid_disk_name): New functions.
[__FreeBSD_kernel__] (grub_util_iterate_devices): Scan for ataraid
(/dev/ar[0-9]+) and ada (/dev/ada[0-9]+) devices using
get_ataraid_disk_name() and get_ada_disk_name().