drm/msm/a6xx: Only print the GMU firmware version once

drm/msm/a6xx: Only print the GMU firmware version once

We only fetch it once from userland, so let's also only notify the
user once and not on every runtime resume.

As you can notice by the tags chain, more than one user found this
annoying.

Reported-by: Jens Glathe <jens.glathe@oldschoolsolutions.biz>
Suggested-by: Abel Vesa <abel.vesa@linaro.org>
Suggested-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/637062/
Signed-off-by: Rob Clark <robdclark@chromium.org>