disas: microblaze: QOMify target specific disas setup

disas: microblaze: QOMify target specific disas setup

Move the target_disas() MB specifics to the QOM disas_set_info hook
and delete the MB specific code in disas.c.

This also now adds support for monitor_disas() to Microblaze.

E.g.
(qemu) xp 0x90000000
0000000090000000: 0x94208001

And before this patch:
(qemu) xp/i 0x90000000
0x90000000: Asm output not supported on this arch

After:
(qemu) xp/i 0x90000000
0x90000000:  mfs    r1, rmsr

Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>