wifi: mt76: connac: rework fields for larger bandwidth support in sta_rec_bf

Rename nrow_bw160 and ncol_bw160 since channel width 320 MHz will share
the same field.
This is a preliminary patch to add mt7996 chipset support.

Signed-off-by: MeiChia Chiu <meichia.chiu@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>