mt76: mt7921: rely on mcu_get_nic_capability

Rely on mcu_get_nic_capability to obtain Tx quota information
for the SDIO device, get PHY capability, MAC address and then we can
totally drop mt7921/eeprom.c and any unnecessary code.

Noting that mt76_connac_mcu_get_nic_capability should be run before set
flag MT76_STATE_MCU_RUNNING being set to setup the proper parameters
like Tx quota control before the device is started to running.

Tested-by: Deren Wu <deren.wu@mediatek.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>