KVM: x86 emulator: Use emulator_write_emulated and not emulator_write_std

emulator_write_std() is not implemented, and calling write_emulated should
work just as well in place of write_std.

Fixes emulator failures with the push r/m instruction.

Signed-off-by: Amit Shah <amit.shah@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

drivers/kvm/x86_emulate.c

@@ -1146,7 +1146,7 @@ done_prefixes:
 			}
 			register_address_increment(_regs[VCPU_REGS_RSP],
 						   -dst.bytes);
-			if ((rc = ops->write_std(
+			if ((rc = ops->write_emulated(
 				     register_address(ctxt->ss_base,
 						      _regs[VCPU_REGS_RSP]),
 				     &dst.val, dst.bytes, ctxt->vcpu)) != 0)