drm/i915: Move vlv cdclk code to .get_display_clock_speed()

We have a standard hook for reading out the current cdclk. Move the VLV
code from valleyview_cur_cdclk() to .get_display_clock_speed().

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --cc drivers/gpu/drm/i915/intel_display.c
Simple merge

diff --cc drivers/gpu/drm/i915/intel_drv.h
Simple merge

diff --cc drivers/gpu/drm/i915/intel_pm.c
Simple merge