VIA VT6420 SATA BIOS

1. 6420Rxxx.rom
   BIOS supports RAID. If subclass code is 0x01 (IDE) before this BIOS executed, BIOS
   will execute nothing.

2. 6420Nxxx.rom
   BIOS does not support RAID functions. If subclass code is 0x01 (IDE) before this BIOS 
   executed, BIOS will execute nothing.
   After BIOS is executed, the subclass code will be set to 0x01 (IDE).