drm/i915: Move WaBarrierPerformanceFixDisable:skl to skl code from chv code

 commit 65ca7514
 Author: Damien Lespiau <damien.lespiau@intel.com>
 Date:   Mon Feb 9 19:33:22 2015 +0000

    drm/i915/skl: Implement WaBarrierPerformanceFixDisable

got misapplied and the code landed in chv_init_workarounds() instead of
the intended skl_init_workarounds(). Move it over to the right place.

Cc: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>