drm/i915: drop DRM_ERROR in intel_fbdev init

This should just be a debug.  Add another debug msg to the inherit path
while we're at it.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=72098


Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>