Fix compatibility issues with cfg80211 on OpenWrt

[CGarces]

Port of #52 by @lyh802

jgrulich reports a bug: The rtl8189 and similar drivers are not compatible with commit mac80211: rebase ontop of v4.18.5 and newer https://forum.openwrt.org/t/the-rtl8189-and-similar-drivers-are-not-compatible-with-commit-mac80211-rebase-ontop-of-v4-18-5-and-newer/31034

refer: https://github.com/abperiasamy/rtl8812AU_8821AU_linux/commit/076ac48d9457e947f50835b38dfc616ac9ab210b saiarcot895 authored and harshavardhana committed on 11 Jan 2019:

• Add explicit memset call to avoid potentially corrupt data. (#277) In kernel 4.19, I saw a kernel crash where kfree was trying to free some garbage pointer. This occurred because this structure wasn't explicitly initialized to 0.