iwlwifi: pcie: make iwl_pcie_cmdq_reclaim static

There's no need for this to be exposed outside of the tx.c
file, make it static.

Change-Id: I41d40008311b108d0578bd2ec73c5477e700a839
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>