btrfs: simplify transid initialization in btrfs_ioctl_wait_sync

A small code simplification, move the default value of transid to its
initialization and remove the else-statement.
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -3133,14 +3133,13 @@ static noinline long btrfs_ioctl_start_sync(struct btrfs_root *root,
 static noinline long btrfs_ioctl_wait_sync(struct btrfs_fs_info *fs_info,
 					   void __user *argp)
 {
-	u64 transid;
+	/* By default wait for the current transaction. */
+	u64 transid = 0;
 
-	if (argp) {
+	if (argp)
 		if (copy_from_user(&transid, argp, sizeof(transid)))
 			return -EFAULT;
-	} else {
-		transid = 0;  /* current trans */
-	}
+
 	return btrfs_wait_for_commit(fs_info, transid);
 }