drm/i915: remove intel_uncore_clear_errors

This was forgotten in

commit 9d1cb914
Author: Paulo Zanoni <paulo.r.zanoni@intel.com>
Date:   Fri Nov 1 13:32:08 2013 -0200

    drm/i915: avoid unclaimed registers when capturing the error state

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>