drm/i915: Simplify scaler init during CRTC HW readout

drm/i915: Simplify scaler init during CRTC HW readout

The crtc state starts out being bzero'd, so no need to clear
scaler_users. Also intel_crtc_init_scalers() knows already which
platforms have scalers, so no need for the platform check here.
Similarly intel_crtc_init_scalers() will init scaler_id as required,
so no need to do it here separately.

Cc: Chandra Konduru <chandra.konduru@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170719225057.20131-2-imre.deak@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>