f2fs: fix false alarm on invalid block address

f2fs_ra_meta_pages can try to read ahead on invalid block address which is
not the corruption case.

Cc: <stable@kernel.org> # v6.9+
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=218770
Fixes: 31f85ccc

 ("f2fs: unify the error handling of f2fs_is_valid_blkaddr")
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>