[][mt76-vendor: update usage message]

[Description]
Change usage message for reminding command chagne.

[Release-log]
N/A

Change-Id: I1955145d6b9c37ae1c5da5a88b359a24b677a6d3
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/4672350
1 file changed