drm/i915: Remove dead code from runtime resume handler

drm/i915: Remove dead code from runtime resume handler

Remove the SNB PCH refclock init call from the runtime resume handler.
I don't think it was actually needed even when we had SNB runtime PM,
and if definitely isn't needed ever since SNB runtime PM was nuked in
commit d4c5636e7447 ("drm/i915: Remove runtime PM for SNB").

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170601183043.28543-1-ville.syrjala@linux.intel.com
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>