drm/i915: Don't warn if the workaround list is empty part 2.

drm/i915: Don't warn if the workaround list is empty part 2.

Extend the same reasoning as in the patch listed below.  It's not an
error for the workaround list to be empty if no workarounds are needed.

    commit e1cd9667e4c4900b89b16c27c0524b082f7af6e7
    Author: Francisco Jerez <currojerez@riseup.net>
    Date:   Wed Oct 7 14:44:01 2015 +0300
        drm/i915: Don't warn if the workaround list is empty.

Signed-off-by: Wayne Boyer <wayne.boyer@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1452129330-3484-2-git-send-email-rodrigo.vivi@intel.com