iwlwifi: mvm: send the STA_HE_CTXT command in AP mode

In AP mode, if AP supports HE (and the STA), send the
STA_HE_CTXT command.

This is needed mainly for PPE (packet extension) params.

Signed-off-by: Shaul Triebitz <shaul.triebitz@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>