drm/msm: rename msm_drv_shutdown() to msm_kms_shutdown()

The msm_drv_shutdown function should only be used in the KMS case.
Rename it accordingly.

Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/561652/


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