macio: Fix timer endianness

The timer registers on our KeyLargo macio emulation are read as byte reversed
from the big endian guest, so we better expose them endian reversed as well.

This fixes initial hickups of booting Mac OS X with -M mac99 for me.

Signed-off-by: Alexander Graf <agraf@suse.de>
Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
