drm/i915: move the {skl, bxt}_{i, uni}nit_cdclk declarations

Move the {skl,bxt}_{i,uni}nit_cdclk declarations to the place where
the intel_cdclk.c functions are declared since these functions have
moved there.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1487712207-17181-1-git-send-email-paulo.r.zanoni@intel.com