Doesn't build with gcc-10

[Gleb Mazovetskiy]

There is a new (forbidden) warning in gcc-10 that looks like this:

rtw_mp.c:1169:3: warning: 'sprintf' argument 3 overlaps destination object 'data' [-Wrestrict]
error, forbidden warning:rtw_mp.c:1169
 1169 |   sprintf(data, "%s%x ", data, psd_data);

I've had to deal with this issue in a fork of the 4.4 kernel and my fix was this e14af2d (#410), though I've noticed the recent mainline commits use a different variant of this fix (keeping track of the end pointer instead of length).

There are dozens of these warnings in all the rtl8xxx repos

[Christian Stewart]

Works now 👍🏽