It is included.
Code:
[/usr/src/sys]$ find . -name GENERIC | xargs grep ataraid
./amd64/conf/GENERIC:device ataraid # ATA RAID drives
./i386/conf/GENERIC:device ataraid # ATA RAID drives
./ia64/conf/GENERIC:device ataraid # ATA RAID drives
FreeBSD 8.0-RC2