iwlwifi: mvm: add LQ flags definitions

Add more bit field definitions used in LQ flags.
Also rename the first bit to a shorter name.

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