drm/msm/adreno: Remove redundant revn param

This just duplicates what is in adreno_info, and can cause confusion if
used before it is set.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/549761/