drm/fb-helper: directly call set_par from the hotplug handler

drm/fb-helper: directly call set_par from the hotplug handler

The idea behind calling down into the driver's ->fb_probe function on each
hotplug seems to be able to reallocate the backing storage (if e.g. a screen
with higher resolution gets added). But that requires quite a bit of work in the
fb helper itself, since currently we limit new screens to the currently
allocated fb. An no kms driver supports fbdev fb resizing.

So don't bother and start to simplify the code by calling drm_fb_helper_set_par
directly from the fbdev hotplug function, since that's the only thing left in
drm_fb_helper_single_fb_probe which does not concern itself with fb allocation
and initial setup. Follow-on patches will streamline the initial setup
code.

Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>