use designated initializer to make adaptability and flexibility for changing struct bus_space.
no functional change.

iMX233/OLinuXino changes from Petri Laskso.
See http://mail-index.netbsd.org/port-arm/2013/10/07/msg002042.html

Add initial support for Freescale i.MX23 application processor.
Contributed by Petri Laakso.