iwlwifi: pcie: initialize trans_pcie->ref_count on configure()

ref_count is currently initialized on start_fw(). This causes
some issues in restart flow, as currently active references
(e.g. unclaimed command) will get cleared, resulting in
invalid reference accounting.

Move the ref_count initialization to the configure() trans op,
so it won't be re-initialized on restart.

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