drm/msm: switch to drmm_mode_config_init()

Switch to drmm_mode_config_init() instead of drm_mode_config_init().
Drop drm_mode_config_cleanup() calls.

Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/561654/


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