KVM: x86: rename EMULATE_DO_MMIO

The next patch will reuse it for other userspace exits than MMIO,
namely debug events.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -5038,11 +5038,11 @@ restart:
 			writeback = false;
 			vcpu->arch.complete_userspace_io = complete_emulated_pio;
 		}
-		r = EMULATE_DO_MMIO;
+		r = EMULATE_USER_EXIT;
 	} else if (vcpu->mmio_needed) {
 		if (!vcpu->mmio_is_write)
 			writeback = false;
-		r = EMULATE_DO_MMIO;
+		r = EMULATE_USER_EXIT;
 		vcpu->arch.complete_userspace_io = complete_emulated_mmio;
 	} else if (r == EMULATION_RESTART)
 		goto restart;