fw_cfg: the I/O port variant expects little-endian

The I/O port variant of fw_cfg is used by sparc64, which is a big-endian machine.
Firmware swaps bytes before sending them to fw_cfg, so we need to unswap them in
the device.

This is only used on sparc64 and on (little-endian) x86, so it does not affect
any other target.  32-bit Sparc and PPC all use memory-mapped fw_cfg.

Reported-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-id: 1375014954-31916-2-git-send-email-pbonzini@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

hw/nvram/fw_cfg.c

diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 0a35015..d0820e5 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -324,7 +324,7 @@
 static const MemoryRegionOps fw_cfg_comb_mem_ops = {
     .read = fw_cfg_comb_read,
     .write = fw_cfg_comb_write,
-    .endianness = DEVICE_NATIVE_ENDIAN,
+    .endianness = DEVICE_LITTLE_ENDIAN,
     .valid.accepts = fw_cfg_comb_valid,
 };