Allwinner sun4i DRM driver fixes
A bunch of fixes that address:
- Compilation errors in various corner cases
- Move to helpers
- Fix the pixel clock computation
- Fix our panel probe
* tag 'sunxi-drm-fixes-for-4.7' of https://git.kernel.org/pub/scm/linux/kernel/git/mripard/linux:
drm: sun4i: do cleanup if RGB output init fails
drm/sun4i: Convert to connector register helpers
drm/sun4i: remove simplefb at probe
drm/sun4i: rgb: panel is an error pointer
drm/sun4i: defer only if we didn't find our panel
drm/sun4i: rgb: Validate the clock rate
drm/sun4i: request exact rates to our parents
drm: sun4i: fix probe error handling
drm: sun4i: print DMA address correctly
drm/sun4i: add COMMON_CLK dependency