fsck.f2fs: declare static function

This avoids the following warning.

mount.c:783:27: warning: SM_I is static but used in inline function
check_seg_range which is not static.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fsck/mount.c b/fsck/mount.c
index 649940d..ae3065f 100644
--- a/fsck/mount.c
+++ b/fsck/mount.c
@@ -778,7 +778,7 @@
 	restore_curseg_summaries(sbi);
 }
 
-inline void check_seg_range(struct f2fs_sb_info *sbi, unsigned int segno)
+static inline void check_seg_range(struct f2fs_sb_info *sbi, unsigned int segno)
 {
 	unsigned int end_segno = SM_I(sbi)->segment_count - 1;
 	ASSERT(segno <= end_segno);