iwlwifi: mvm: don't use cts to self

The current fw doesn't currently support cts to self. There
is a bug in the fw that prevents us from using cts to self.
Use full protection (including RTS) for now.

Signed-off-by: Dor Shaish <dor.shaish@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>