drm/i915: Move the SKL DPLL0 VCO computation into intel_dp_compute_config()

drm/i915: Move the SKL DPLL0 VCO computation into intel_dp_compute_config()

Shared plls won't get assigned until the .compute_clocks() hook gets
called, which happens from the crtc .atomic_check hook. That's too late
as the cdclk computation has already happened. So let's move the DPLL0
VCO computation into intel_dp_compute_config() so that it's done when
the cdclk computation happens. Also only do it for eDP since we only
pick DPLL0 for eDP.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463172100-24715-4-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>