f2fs: new helper cur_cp_crc() getting crc in f2fs_checkpoint

There are four places that getting the crc value in f2fs_checkpoint,
just add a new helper cur_cp_crc for them.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 04d7c24..0339daf 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -683,8 +683,7 @@
 		return -EINVAL;
 	}
 
-	crc = le32_to_cpu(*((__le32 *)((unsigned char *)*cp_block
-							+ crc_offset)));
+	crc = cur_cp_crc(*cp_block);
 	if (!f2fs_crc_valid(sbi, crc, *cp_block, crc_offset)) {
 		f2fs_msg(sbi->sb, KERN_WARNING, "invalid crc value");
 		return -EINVAL;