iwlwifi: mvm: set MAC_FILTER_IN_11AX in AP mode

In AP mode, if AP supports 11ax, add the MAC_FILTER_IN_11AX
flag in MAC_CTXT command (needed for various 11ax stuff).

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