The generic EWMA code cannot deal with negative numbers, so convert signal
to a positive number before adding it
Fixes mt76x2 AGC tuning
Signed-off-by: Felix Fietkau <nbd@nbd.name>
This will be used by drivers for MT76x2e, MT7603e and MT7628
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>