f2fs: clean up with a macro

This patch adds GET_BLKOFF_FROM_SEG0 to clean up some codes.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
index f1b0b89..bda04a0 100644
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -218,8 +218,7 @@
 {
 	struct seg_entry *sentry;
 	unsigned int segno = GET_SEGNO(sbi, blkaddr);
-	unsigned short blkoff = GET_SEGOFF_FROM_SEG0(sbi, blkaddr) &
-					(sbi->blocks_per_seg - 1);
+	unsigned short blkoff = GET_BLKOFF_FROM_SEG0(sbi, blkaddr);
 	struct f2fs_summary sum;
 	nid_t ino, nid;
 	void *kaddr;