ramips: mt76x8: select only the matching mt76 driver

ramips: mt76x8: select only the matching mt76 driver

Select the matching mt76 driver for the PCI wireless of the following
devices:

 - HiWiFi HC5861B
 - Mercury MAC1200R v2.0
 - Netgear AC1200 R6120
 - Buffalo WCR-1166DS
 - ZyXEL Keenetic Extra II
 - Wavlink WL-WN575A3

Because every device has selected the corresponding mt76 driver, we can
include kmod-mt7603 instead of the mt76 metapackage, which used for the
wireless of the mt7628 and mt7688 WiSoC.

Signed-off-by: Chen Minqiang <ptpt52@gmail.com>
[select kmod-mt7603 as target default package, add wireless driver for
WL-WN575A3]
Signed-off-by: Mathias Kresin <dev@kresin.me>