wifi: mt76: support power delta calculation for 5 TX paths

wifi: mt76: support power delta calculation for 5 TX paths

One variant of MT7992 has 5 TX paths, so extend the power delta function
to support it. Also, rename nss_delta to path_delta since the value is
based on the number of TX paths rather tha the number of spatial streams.
(path delta [0.5 dBm] = 10 * log(path number) [dBm] * 2)

Co-developed-by: StanleyYP Wang <StanleyYP.Wang@mediatek.com>
Signed-off-by: StanleyYP Wang <StanleyYP.Wang@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Link: https://patch.msgid.link/20250515032952.1653494-9-shayne.chen@mediatek.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>