mt76: mt7996: select required kernel and hostap options

mt76: mt7996: select required kernel and hostap options

Select DRIVER_11AX_SUPPORT and KERNEL_RELAY also for kmod-mt7996 to
prevent build failure if only this driver is selected during build and
end up with (most) required hostap features (IEEE 802.11be rates are not
yet supported).

Reported-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
(cherry picked from commit 83311b747012e0675f96af18793e92cb8320c707)
Link: https://github.com/openwrt/openwrt/pull/15898
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>