wifi: mt76: mt792x: re-register CHANCTX_STA_CSA only for the mt7921 series

CSA is currently not supported on mt7925, so CSA is only registered for
the mt7921 series

Cc: stable@vger.kernel.org
Fixes: 8aa2f592 ("wifi: mt76: mt7921: introduce CSA support")
Signed-off-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
Link: https://patch.msgid.link/20250313054044.2638837-1-mingyen.hsieh@mediatek.com


Signed-off-by: Felix Fietkau <nbd@nbd.name>