iwlwifi: pcie: fix unused variable gcc warning

In iwl_pcie_int_cause_non_ict, trans_pcie is used for lockdep
purposes only. Since this might not be enabled, trans_pcie
finds itself without user leading to a complaint from gcc.
Avoid using trans_pcie by inlining IWL_TRANS_GET_PCIE_TRANS.

Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>