drm/i915: Shovel hw setup code out of hsw_crtc_mode_set

Again the same story: This code just transform sw state from the pipe
config into hardware state. And again we can't move the pll code, but
this time around because the state isn't properly tracked in the pipe
config.

Reviewed-by: Shobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>