KVM: x86 emulator: Move string pio emulation into emulator.c

Currently emulation is done outside of emulator so things like doing
ins/outs to/from mmio are broken it also makes it hard (if not impossible)
to implement single stepping in the future. The implementation in this
patch is not efficient since it exits to userspace for each IO while
previous implementation did 'ins' in batches. Further patch that
implements pio in string read ahead address this problem.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>