Fix ignored return value in virt/kvm/ioregion.c

In virt/kvm/ioregion.c the return values are ignored on two occasions.
This causes compiler warnings that let the kernel build fail. Both are
now fixed by just putting the value into some variable that was around.

virt/kvm/ioregion.c

@@ -150,7 +150,7 @@ ioregion_read(struct kvm_vcpu *vcpu, struct kvm_io_device *this, gpa_t addr,
 		return -EOPNOTSUPP;
 	}
 
-	mutex_lock_interruptible(&p->ctx->mutex);
+	ret = mutex_lock_interruptible(&p->ctx->mutex);
 
 	ret = kernel_write(p->wf, cmd, sizeof(*cmd), 0);
 	if (ret != sizeof(*cmd)) {
@@ -217,7 +217,7 @@ ioregion_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this, gpa_t addr,
 		return -EOPNOTSUPP;
 	}
 
-	mutex_lock_interruptible(&p->ctx->mutex);
+	ret = mutex_lock_interruptible(&p->ctx->mutex);
 
 	ret = kernel_write(p->wf, cmd, sizeof(*cmd), 0);
 	if (ret != sizeof(*cmd)) {