f2fs: fix incorrect return value in f2fs_sanity_check_ckpt()

As Pavel Machek reported in [1]

This code looks quite confused: part of function returns 1 on
corruption, part returns -errno. The problem is not stable-specific.

[1] https://lkml.org/lkml/2021/9/19/207

Let's fix to make 'insane cp_payload case' to return 1 rater than
EFSCORRUPTED, so that return value can be kept consistent for all
error cases, it can avoid confusion of code logic.

Fixes: 65ddf656

 ("f2fs: fix to do sanity check for sb/cp fields correctly")
Reported-by: Pavel Machek <pavel@denx.de>
Reviewed-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>