mediatek: mt7622: add Adtran SmartRG SDG-841t6 device
Specification
SoC: MediaTek MT7622A (2x Cortex-A53)
RAM: NANYA NT5CC256M16ER-EK (512 MiB)
MMC: Kioxia THGBMNG5D1LBAIT (4 GiB)
ETH0: Intel/MaxLinear GPY211 (2500M/1000M/100M/10M)
ETH1: Lantiq/Intel/MaxLinear PEF7071/GPY111 (1000M/100M/10M)
WLAN0: MediaTek MT7915E + MT7975D 2T2R 802.11bgn/ax (2.4G)
2T2R 802.11an/ac/ax (5G L)
WLAN1: MediaTek MT7915E + MT7975A 4T4R 802.11an/ac/ax (5G H)
BT: BT5 provided by MT7915E+MT7975D (missing firmware)
Signed-off-by: Daniel Golle <daniel@makrotopia.org>