actually with the latest kernel (and correction) it shouldn't be needed to do this anymore (can be found on the latest github...)
Okay, I tested it and can confirm that it also works, but only with 15.4 amdocl.dll (may be with later versions too). With 14.4 it does not. And it started to work only when I replaced kernel files from here
https://github.com/djm34/sgminer/tree/master/kernelAnd 7950 started to hash a bit faster.
Thank you!