f2fs: clean up with is_valid_blkaddr()

- rename is_valid_blkaddr() to is_valid_meta_blkaddr() for readability.
- introduce is_valid_blkaddr() for cleanup.

No logic change in this patch.

Signed-off-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 1fb8385..d535d60 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1895,7 +1895,7 @@
 	struct seg_entry *se;
 	bool is_cp = false;
 
-	if (blkaddr == NEW_ADDR || blkaddr == NULL_ADDR)
+	if (!is_valid_blkaddr(blkaddr))
 		return true;
 
 	down_read(&sit_i->sentry_lock);
@@ -2960,7 +2960,7 @@
 {
 	struct page *cpage;
 
-	if (blkaddr == NEW_ADDR || blkaddr == NULL_ADDR)
+	if (!is_valid_blkaddr(blkaddr))
 		return;
 
 	cpage = find_lock_page(META_MAPPING(sbi), blkaddr);