kvm/ppc/mpic: fix missing unlock in set_base_addr()

Add the missing unlock before return from function set_base_addr()
when disables the mapping.

Introduced by commit 5df554ad
(kvm/ppc/mpic: in-kernel MPIC emulation)
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/kvm/mpic.c

@@ -1486,8 +1486,8 @@ static int set_base_addr(struct openpic *opp, struct kvm_device_attr *attr)
 
 	map_mmio(opp);
 
-	mutex_unlock(&opp->kvm->slots_lock);
 out:
+	mutex_unlock(&opp->kvm->slots_lock);
 	return 0;
 }