memory: Introduce DEVICE_HOST_ENDIAN for ram device

memory: Introduce DEVICE_HOST_ENDIAN for ram device

At the moment ram device's memory regions are DEVICE_NATIVE_ENDIAN. It's
incorrect. This memory region is backed by a MMIO area in host, so the
uint64_t data that MemoryRegionOps read from/write to this area should be
host-endian rather than target-endian. Hence, current code does not work
when target and host endianness are different which is the most common case
on PPC64. To fix it, this introduces DEVICE_HOST_ENDIAN for the ram device.

This has been tested on PPC64 BE/LE host/guest in all possible combinations
including TCG.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com>
Message-Id: <1488171164-28319-1-git-send-email-xyjxie@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>