kernel - Change legacy MBR partition type from 0xA5 to 0x6C
* Should have done this years ago but finally change the legacy MBR
partition type DragonFlyBSD uses from 0xA5 (which was shared with
FreeBSD), to something different 0x6C.
* Makes it less confusing for Grub.
* Does not change EFI boot, which uses 16-byte UUIDs (we already have
our own) and does not use 8-bit partition ids.
* Boot code and kernel now recognize both 0xA5 and 0x6C. Existing users
do *NOT* need to reinstall their boot code.