MIPS Magnum: fix memory-mapped i8042

MIPS Magnum: fix memory-mapped i8042

Current implementation of memory-mapped i8042 controller is atm
implemented with an interface shift (it_shift) parameter, like most all
memory-mapped devices in Qemu.
However, this isn't suitable for MIPS Magnum, where i8042 controller is at
0x80005000 up to 0x80005fff.

Thomas Bogendoerfer (from #mipslinux) tested the behaviour of a real
machine, and found that odd addresses are for status/command register, and
even addresses for data register.

Attached patch implements this behaviour by replacing the it_shift
parameter by a mask one.
Incidentally, keyboard now works on OpenBSD 2.3, which accesses i8042
controller at 0x80005060 and 0x80005061.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5962 c046a42c-6fe2-441c-8c8c-71466251a162