iwlwifi: mvm: support VHT in rs

Enable rs algorithm to use VHT rates and use 80Mhz.
This enables reaching VHT rates which wasn't possible.

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