kernel: mtdsplit_h3c_vfs: return 0 for non-fatal errors

kernel: mtdsplit_h3c_vfs: return 0 for non-fatal errors

Since Linux 6.7, introduced with commit 5c2f7727d437 ("mtd: mtdpart:
check for subpartitions parsing result"), errors during subpartition
parsing cause all MTD partitions to be torn down.

Since the current mtdsplit driver for devices using H3C VFS returns
-EINVAL if it does not find a file system containing an OpenWrt image,
this makes initial installation of OpenWrt impossible.

Work around this by returning 0 when the file system contains unexpected
data. Also print a message in this case to show what is going on.

Signed-off-by: Jan Hoffmann <jan@3e8.eu>
Link: https://github.com/openwrt/openwrt/pull/19475
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>