net80211: fix ieee80211_htrateset setup, return EINVAL for an unsupported ucast/mcast/mgmt HT rate

[avos]

Summary

• Init global ieee80211_htrateset only once; neither ic_htcaps nor ic_txstream is changed when device is attached.
• Move global ieee80211_htrateset structure to ieee80211com; there was a possible data race when more than 1 wireless device is used simultaneously;
• Discard unsupported rates in ieee80211_ioctl_settxparams(); otherwise, an unsupported value may break connectivity (actually, 'ifconfig wlan0 ucastrate 8' for RTL8188EU results in immediate disconnect + infinite 'device timeout's' after it)

Test Plan

Tested with

• Intel 6205, STA mode.
• RTL8821AU, STA mode.

[avos]

Init htrateset a bit later

[adrian]

I like this. Good catch!