wifi: iwlwifi: pcie: move ltr_enabled to the specific transport

wifi: iwlwifi: pcie: move ltr_enabled to the specific transport

Currently it is under iwl_trans, which is the bus agnostic part of the
transport. But really it is relevant for pcie only, so move it to the
iwl_trans_pcie and export it via an API to the opmode.

Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250909061931.9f9dc80ab06c.I3eeca8b17abeba6ed30f0d681518c81ede0acf30@changeid