Booting from a md raid device on powerpc

Apparently, nobody has ever tried to do this so far, since the mac partition handling code in the Linux kernel had no provisions for enabling auto-detection of md software raid.

I've now written patch for Linux 2.6.8, available at implementing this feature. All you need to do is apply that patch, and make sure your md partitions have the type 'Linux_raid_autodetect' in the mac partition table.