btrfs-progs: help: fix printing of aliased commands

The help string for aliased commands is glued on one line.  This
happened for device delete/remove.

Signed-off-by: David Sterba <dsterba@suse.com>

help.c

@@ -148,6 +148,8 @@ static void usage_command_group_internal(const struct cmd_group *grp, int full,
 
 			usage_command_internal(cmd->usagestr, cmd->token, full,
 					       1, cmd->flags & CMD_ALIAS, outf);
+			if (cmd->flags & CMD_ALIAS)
+				putchar('\n');
 			continue;
 		}