f2fs: introduce f2fs_cp_error for readability

This patch adds f2fs_cp_error for readability.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index f7bc34c..6a15318 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -162,7 +162,7 @@
 		goto redirty_out;
 
 	/* Should not write any meta pages, if any IO error was occurred */
-	if (unlikely(is_set_ckpt_flags(F2FS_CKPT(sbi), CP_ERROR_FLAG)))
+	if (unlikely(f2fs_cp_error(sbi)))
 		goto no_write;
 
 	f2fs_wait_on_page_writeback(page, META);
@@ -933,7 +933,7 @@
 	/* Here, we only have one bio having CP pack */
 	sync_meta_pages(sbi, META_FLUSH, LONG_MAX);
 
-	if (!is_set_ckpt_flags(ckpt, CP_ERROR_FLAG)) {
+	if (!f2fs_cp_error(sbi)) {
 		clear_prefree_segments(sbi);
 		release_dirty_inode(sbi);
 		F2FS_RESET_SB_DIRT(sbi);