mt76x2: remove unnecessary MT_TX_ALC_CFG_4 configuration

Remove unnecessary MT_TX_ALC_CFG_4 configuration since the register value
will be properly set according to the usage of an external power amplifier

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Acked-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>