bios: Add fast variant of SeaBIOS for use with -kernel on x86.

bios: Add fast variant of SeaBIOS for use with -kernel on x86.

This commit adds a fast variant of SeaBIOS called 'bios-fast.bin'.

It's designed to be the fastest (also the smallest, but that's not the
main aim) SeaBIOS that is just enough to boot a Linux kernel using the
-kernel option on i686 and x86_64.

This commit does not modify the -kernel option to use this.  You have
to specify it by doing something like this:

  -kernel vmlinuz -bios bios-fast.bin

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>