wifi: mt76: mt7915: add back 160MHz channel width support for MT7915

A number of users reported that this support was working fine before
it got removed. Add it back, but leave out the unsupported 80+80 mode.

Fixes: ac922bd6 ("wifi: mt76: mt7915: remove BW160 and BW80+80 support")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230301163739.52314-1-nbd@nbd.name