iwlwifi: consolidate hw scheduler configuration code

Configuring the hw scheduler during queue enablement is done by
writing the appropriate values to the scheduler peripherals, and
it is essentially the same for all buses.

Whenever writing is done via the standard iwl_write_prph, we can
avoid duplicating the code for each bus. Those operations are
queue deactivation, RA/TID mapping, chain-building settings,
enabling/disabling aggregations and activating/deactivating the
TX FIFOs.

Consolidate this code using static inlines in a new header file.

Signed-off-by: Avri Altman <avri.altman@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>