KVM: x86 emulator: Fix HLT instruction

This patch fixes issue encountered with HLT instruction
under FreeDOS's HIMEM XMS Driver.

The HLT instruction jumped directly to the done label and
skips updating the EIP value, therefore causing the guest
to spin endlessly on the same instruction.

The patch changes the instruction so that it writes back
the updated EIP value.

Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>