target-ppc: Introduce unrealizefn for PowerPCCPU

Use it to clean up the opcode table, resolving a former TODO from Jocelyn.
Also switch from malloc() to g_malloc().

Signed-off-by: Andreas Färber <afaerber@suse.de>
mpc8544_guts: Fix MemoryRegion name

6544 -> 8544

Signed-off-by: Andreas Färber <afaerber@suse.de>
mpc8544_guts: QOM'ify

Introduce type constant and cast macro.

Signed-off-by: Andreas Färber <afaerber@suse.de>
mpc8544_guts: Convert to QOM realize

Signed-off-by: Andreas Färber <afaerber@suse.de>