drm: Pull together probe + setup for drm_fb_helper

drm_fb_helper_probe_connector_modes() is always called before
drm_setup_crtcs(), so just move the call into drm_setup_crtcs for a
small bit of code compaction.

Note that register_framebuffer will do a modeset (when fbcon is enabled)
and hence must be moved out of the critical section. A follow-up patch
will add new locking for the fb list, hence move all the related
registration code together.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20161129120217.7344-2-chris@chris-wilson.co.uk