Function zx_find_crtc() does the exactly same thing as what crtc helper
drm_crtc_from_index() provides.  Use the helper to save some code.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483015290-16660-3-git-send-email-shawnguo@kernel.org

It adds the initial ZTE VOU display controller DRM driver.  There are
still some features to be added, like overlay plane, scaling, and more
output devices support.  But it's already useful with dual CRTCs and
HDMI monitor working.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>