APPLIED: [X/B][SRU][CVE-2018-21008] rsi: add fix for crash during assertions

[Kleber Souza]

On 26.09.19 20:56, Connor Kuehl wrote:
> https://people.canonical.com/~ubuntu-security/cve/2018/CVE-2018-21008.html
> 
> From the above link:
> 
> 	"An issue was discovered in the Linux kernel before 4.16.7. A use-after-free
> 	can be caused by the function rsi_mac80211_detach in the file
> 	drivers/net/wireless/rsi/rsi_91x_mac80211.c."
> 
> Clean cherry pick for Bionic, only required an offset adjustment for Xenial.
> 

Applied to {xenial,bionic}/master-next branches.

Thanks,
Kleber