f2fs: return a default value for non-void function

This patch resolves a build warning reported by kbuild test robot.

"
fs/f2fs/segment.c: In function '__get_segment_type':
fs/f2fs/segment.c:806:1: warning: control reaches end of non-void
function [-Wreturn-type]
"
Signed-off-by: NJaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/segment.c

@@ -791,11 +791,10 @@ static int __get_segment_type(struct page *page, enum page_type p_type)
 		return __get_segment_type_2(page, p_type);
 	case 4:
 		return __get_segment_type_4(page, p_type);
-	case 6:
-		return __get_segment_type_6(page, p_type);
-	default:
-		BUG();
 	}
+	/* NR_CURSEG_TYPE(6) logs by default */
+	BUG_ON(sbi->active_logs != NR_CURSEG_TYPE);
+	return __get_segment_type_6(page, p_type);
 }
 
 static void do_write_page(struct f2fs_sb_info *sbi, struct page *page,

fs/f2fs/super.c

@@ -302,7 +302,7 @@ static int parse_options(struct f2fs_sb_info *sbi, char *options)
 		case Opt_active_logs:
 			if (args->from && match_int(args, &arg))
 				return -EINVAL;
-			if (arg != 2 && arg != 4 && arg != 6)
+			if (arg != 2 && arg != 4 && arg != NR_CURSEG_TYPE)
 				return -EINVAL;
 			sbi->active_logs = arg;
 			break;