iwlwifi: mvm: Add P2P client snoozing

Enable snoozing and U-APSD on P2P client. The firwmare will
support this only if the BSS vif is not associated.
Make this configurable by a constant variable and disable
it by default.

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