ath: do not apply broken power limits with ATH_USER_REGD

If a device uses the default EEPROM code, typically only the main CTLs
are valid, and they do not apply properly when switching to a different
regulatory domain. If the regdomain deviates from the EEPROM one, force
the world roaming regdomain to ensure that power limits are sane

Signed-off-by: Felix Fietkau <nbd@nbd.name>