make sure that you have extracted the SDK License.
(I think this was like, cd /; tar xvf /path/to/amdsdk/icd-registration.tgz)
atiocl32.icd atiocl64.icd nvidia.icd
I just added /opt/AMD-APP-SDK-v2.4-lnx64/lib/x86_64 to my /etc/ld.so.conf.
Seems to work too. (read the pdfs in the doc folder of the sdk if in doubt)
My .bashrc:
export ATISTREAMSDKROOT=/opt/ati-stream-sdk-v2.1-lnx64
export ATISTREAMSDKSAMPLESROOT=/opt/ati-stream-sdk-v2.1-lnx64
Why are you running 11.8? I haven't tried 11.8, but 11.7 was buggy.
11.6 still seems to be the sweet spot on Linux, and it gets along just fine with 2.1 SDK
Also having nvidia drivers installed could be causing a problem, you should try removing them if OpenCL still isn't recognized after installing 11.6