wifi: mt76: mt7915: fix mt7915_mac_set_timing()

wifi: mt76: mt7915: fix mt7915_mac_set_timing()

[ Upstream commit c039210bca8a28e35e580a2bfb9f78ec5a45835f ]

Correct mac timiing settings for different hardware generations.
This improves 40-60Mbps performance.

Fixes: a8a36c7c499e ("mt76: mt7915: update mac timing settings")
Reported-By: Carson Vandegriffe <carson.vandegriffe@candelatech.com>
Tested-by: Chad Monroe <chad.monroe@smartrg.com>
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Sasha Levin <sashal@kernel.org>