add ARMADA XP's Soc internal bus(Mbus) address decoder initialization function.
some versions of u-boot initializes the address decoder incorrectly(probably
these values are come from Kirkwood SoC or older.) the codes generates
SoC's default address spaces and some modifications for NetBSD's assumption.

add error interrupt definitions, interrupt name strings for 'vmstat -e',
verbose output of Mbus settings for such low-level debugging of SoC.

(hsuenaga)