drm/i915: fixup l3 parity sysfs access check

When l3 parity support for Haswell was enabled in

commit f27b9265
Author: Ben Widawsky <benjamin.widawsky@intel.com>
Date:   Tue Jul 24 20:47:32 2012 -0700

    drm/i915: Expand DPF support to Haswell

no one noticed that the patch which introduced this macro

commit e1ef7cc2


Author: Ben Widawsky <benjamin.widawsky@intel.com>
Date:   Tue Jul 24 20:47:31 2012 -0700

    drm/i915: Macro to determine DPF support

missed one spot. Fix this.

Cc: Ben Widawsky <benjamin.widawsky@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=57441
Reviewed-by: Ben Widawsky <benjamin.widawsky@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>