drm/msm: Add obj flags to gpu devcoredump

When debugging faults, it is useful to know how the BO is mapped (cached
vs WC, gpu readonly, etc).

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
Acked-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/593854/