[MTD] Add Resident Flash Disk (RFD) support

This type of flash translation layer (FTL) is used by the Embedded BIOS
by General Software. It is known as the Resident Flash Disk (RFD), see:

http://www.gensw.com/pages/prod/bios/rfd.htm



Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>