target-s390: add firmware code
This patch adds a firmware blob to the S390 target. The blob is a simple
implementation of a virtio client that tries to read the second stage
bootloader from sectors described as of offset 0x20 in the MBR.
In combination with an updated zipl this allows for booting from virtio
block devices. This firmware is built from the same sources as the second
stage bootloader. You can find a virtio capable s390-tools in this repo:
git://repo.or.cz/s390-tools.git
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>