drm/armada: Convert the probe function to the generic drm_of_component_probe()

drm/armada: Convert the probe function to the generic drm_of_component_probe()

The armada DRM driver keeps some old platform data compatibility in the
probe function that makes moving to the generic drm_of_component_probe()
a bit more complicated that it should. Refactor the probe function to do
the platform_data processing after the generic probe (and only if that
fails). This way future cleanup can further remove support for it.

Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1445332995-11212-5-git-send-email-Liviu.Dudau@arm.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>