well, first sorry for my English, can you upload the rom file with the driver already modified for mxq S805 ?Many users have same problem, it is due to different WiFi modules used.
Solution is very easy - just replace drivers in your firmware system/lib with correct one.
I have same problem with many custom and original ROM's using on my MXQ S805, in my situation WiFi works fine when drivers replaced to RTL8188EVT.
That's it.
tried to put this one and was no wifi and ethernet