mt76: mt7915: fix sta_rec_wtbl tag len

[ Upstream commit afa0370f ]

Fix tag len error for sta_rec_wtbl, which causes fw parsing error for
the tags placed behind it.

Fixes: e57b7901 ("mt76: add mac80211 driver for MT7915 PCIe-based chipsets")
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Sasha Levin <sashal@kernel.org>