mediatek-drm build dependency fixes
- add COMMON_CLK dependency for mipi-tx PLL
- add OF dependency for mtk_drm_drv
- add ARM_SMCCC dependency for mtk-hdmi
* tag 'mediatek-drm-fixes-2016-08-12' of git://git.pengutronix.de/git/pza/linux:
drm/mediatek: add ARM_SMCCC dependency
drm/mediatek: add CONFIG_OF dependency
drm/mediatek: add COMMON_CLK dependency