batman-adv: use return instead of continue in the migration script

batman-adv: use return instead of continue in the migration script

proto_batadv_to_batadv_hardif() uses continue to skip a section, but
there is no loop in the function itself. POSIX leaves continue
without an enclosing loop in the current function unspecified; ash
walks the dynamic call stack and lands on the loop inside
config_foreach, which happens to produce the intended behaviour.

Use return, which expresses the intent directly and does not depend
on how config_foreach is implemented.

Reported-by: openwrt-ai[bot]
Signed-off-by: Josef Schlehofer <redacted>
Co-authored-by: Claude Fable 5 <redacted>