f2fs: use true and false for boolean values

Return statements in functions returning bool should use true or false
instead of an integer value.

This issue was detected with the help of Coccinelle.
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -1334,7 +1334,7 @@ static inline bool is_idle(struct f2fs_sb_info *sbi)
 	struct request_list *rl = &q->root_rl;
 
 	if (rl->count[BLK_RW_SYNC] || rl->count[BLK_RW_ASYNC])
-		return 0;
+		return false;
 
 	return f2fs_time_over(sbi, REQ_TIME);
 }
@@ -3400,7 +3400,7 @@ static inline bool f2fs_may_encrypt(struct inode *inode)
 
 	return (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode));
 #else
-	return 0;
+	return false;
 #endif
 }