Merge branch 'sfc-siena-fix-some-efx_separate_tx_channels-errors'

Íñigo Huguet says:

====================
sfc/siena: fix some efx_separate_tx_channels errors

Trying to load sfc driver with modparam efx_separate_tx_channels=1
resulted in errors during initialization and not being able to use the
NIC. This patches fix a few bugs and make it work again.

This has been already done for sfc, do it also for sfc_siena.
====================

Link: https://lore.kernel.org/r/20220601063603.15362-1-ihuguet@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>