iwlwifi: mvm: rs: organize and cleanup consts

Organize and cleanup the consts used by rs.
This is part of making some of these configurable.

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