[][mac80211][mt76][update mpdu density setting]

[Description]
Fix MPDU density setting to the same setting as jedi.
For mt7915, MMSS is 4.
For mt7986, MMSS is 2.

[Release-log]
N/A

Change-Id: Ic3e0730e4f76d25fa87dd6aa8b16d204cd2bbcf9
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7535571
1 file changed