drm/msm/adreno: Introduce gmu_chipid for a740 & a750

To simplify, introduce the new gmu_chipid for a740 & a750 GPUs.

Signed-off-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/601396/


Signed-off-by: Rob Clark <robdclark@chromium.org>