target-mips: DMA support for RC4030 chipset

Attached patch implements DMA support to RC4030 chipset and simplifies
jazz IO part (at 0xf0000000), where registers contain 16 bit values.
Config register has not a clear meaning (only one value is always valid,
and sometimes another one), so use a magic value instead.
The patch also wires DMA transfers for the SCSI adapter in the Jazz
emulation (Mips Magnum 4000 and Acer Pica 61).

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@6145 c046a42c-6fe2-441c-8c8c-71466251a162
