[coreboot] SeaBIOS supports usb drives

[Kevin O'Connor]

Hi,

The latest SeaBIOS git now has preliminary support for booting from
USB drives.  For info on obtaining SeaBIOS, see:

http://seabios.org/Download

I have used this support to successfully boot my epia-cn machine from
both a USB flash drive and a USB cdrom drive.

Currently only UHCI USB controllers are supported.  The timing and
error handling is still being worked on, and one may see sporadic boot
failures.  There is no support for disk writing at this time.

Cheers,
-Kevin