net: ipa: don't configure IDLE_INDICATION on v3.1

IPA v3.1 doesn't support the IDLE_INDICATION_CFG register, this was
causing a harmless splat in ipa_idle_indication_cfg(), add a version
check to prevent trying to fetch this register on v3.1

Fixes: 6a244b75 ("net: ipa: introduce ipa_reg()")
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Tested-by: Jami Kettunen <jami.kettunen@somainline.org>
Link: https://lore.kernel.org/r/20221024234850.4049778-1-caleb.connolly@linaro.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>