kvm__emulate_io: Don't call br_read_unlock() twice on IO error

The IO error path in kvm__emulate_io would call br_read_unlock(), then
goto error, which would call br_read_unlock() again.  Refactor the
control flow to have only one exit path and one call to
br_read_unlock().

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/ioport.c b/ioport.c
index 81a747d..8c55a84 100644
--- a/ioport.c
+++ b/ioport.c
@@ -185,7 +185,7 @@
 	br_read_lock();
 	entry = ioport_search(&ioport_tree, port);
 	if (!entry)
-		goto error;
+		goto out;
 
 	ops	= entry->ops;
 
@@ -198,14 +198,11 @@
 		ptr += size;
 	}
 
+out:
 	br_read_unlock();
 
-	if (!ret)
-		goto error;
-
-	return true;
-error:
-	br_read_unlock();
+	if (ret)
+		return true;
 
 	if (kvm->cfg.ioport_debug)
 		ioport_error(port, data, direction, size, count);