dev: Default the VirtIO device's endianness to little.

We only use VirtIO on simulated systems that are little endian now, and
if we use them on big endian systems in the future, the user can
explicitly configure that, rather than have it automatically change
which might be surprising.

Change-Id: Ie8de22541d409f2b2e5544237f472dae6714b437
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52105
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/dev/virtio/VirtIO.py

@@ -51,7 +51,7 @@ class VirtIODeviceBase(SimObject):
     subsystem = Param.UInt8(0x00, "VirtIO subsystem ID")
 
     system = Param.System(Parent.any, "system object")
-    byte_order = Param.ByteOrder(Parent.byte_order, "Device byte order")
+    byte_order = Param.ByteOrder('little', "Device byte order")
 
 class VirtIODummyDevice(VirtIODeviceBase):
     type = 'VirtIODummyDevice'