iwlwifi: give PCIe its own lock

Instead of using a global lock, the PCIe transport
can use an own lock for its IRQ. This will make it
possible to not disable IRQs for the shared lock.
The lock is currently used throughout the code but
this can be improved even further by splitting up
the locking for the queues.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Wey-Yi W Guy <wey-yi.w.guy@intel.com>