f2fs: make local functions static

Fixes the following sparse warnings:

fs/f2fs/segment.c:887:6: warning:
 symbol '__check_sit_bitmap' was not declared. Should it be static?
fs/f2fs/segment.c:1327:6: warning:
 symbol 'f2fs_wait_discard_bio' was not declared. Should it be static?
fs/f2fs/super.c:1661:5: warning:
 symbol 'f2fs_get_projid' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 33cdf6e..fd3aa1a 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -884,7 +884,7 @@
 	bio_put(bio);
 }
 
-void __check_sit_bitmap(struct f2fs_sb_info *sbi,
+static void __check_sit_bitmap(struct f2fs_sb_info *sbi,
 				block_t start, block_t end)
 {
 #ifdef CONFIG_F2FS_CHECK_FS
@@ -1324,7 +1324,7 @@
 }
 
 /* This should be covered by global mutex, &sit_i->sentry_lock */
-void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
+static void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
 {
 	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
 	struct discard_cmd *dc;