[][MAC80211][misc][Change the HEMU name]

[Description]
Change the MU name from HEMU to MU to forward-compatibility.

[Release-log]
N/A

Change-Id: I1cf490ab17976416d8013323e7f8606a740da26b
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7153415
17 files changed