wifi: iwlwifi: move STEP config into trans->conf

wifi: iwlwifi: move STEP config into trans->conf

This really belongs there, it's needed early, so move it. Remove
the related but dead iwl_trans_pcie_ctx_info_gen3_set_step() while
at it. In iwlmld move the calls since they do part of the trans
configuration.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250504132447.a4681ee11dd7.I6434a13d51932e984bb07695bc1cb931ebdcd27c@changeid