target-ppc: Get MMU state on register sync

target-ppc: Get MMU state on register sync

While x86 only needs to sync cr0-4 to know all about its MMU state and enable
qemu to resolve virtual to physical addresses, we need to sync all of the
segment registers on PPC to know which mapping we're in.

So let's grab the segment register contents to be able to use the "x" monitor
command and also enable the gdbstub to resolve virtual addresses.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>