erofs: fix ztailpacking on > 4GiB filesystems

z_idataoff here is an absolute physical offset, so it should use
erofs_off_t (64 bits at least). Otherwise, it'll get trimmed and
cause the decompresion failure.

Link: https://lore.kernel.org/r/20220222033118.20540-1-hsiangkao@linux.alibaba.com
Fixes: ab92184f

 ("erofs: add on-disk compressed tail-packing inline support")
Reviewed-by: Yue Hu <huyue2@yulong.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>