qemu: add fw_cfg files support

Qemu can provide files using the firmware config interface.
This is used to pass config options, virtual machine config
info and option roms into the guest.

This patch adds support for reading the file index and loading
files from qemu.

Change-Id: I57d4a734527c4117239f355121cf1fb8a390ab0d
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-on: http://review.coreboot.org/4029
Tested-by: build bot (Jenkins)
2 files changed