virtio-blk doesn't work on cross-endian configuration, as endianness is
not handled correctly.
This patch adds missing endianness conversions to make virtio-blk
working. Tested on the following configurations:
- i386 guest on x86_64 host
- ppc guest on x86_64 host
- i386 guest on mips host
- ppc guest on mips host
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>