drm/i915: Enable some sysfs stuff without CONFIG_PM

The original patch was actually incorrect in stubbing out the sysfs for
l3 parity.
commit 5ab3633d
Author: Hunt Xu <mhuntxu@gmail.com>
Date:   Sun Jul 1 03:45:07 2012 +0000

    drm/i915: make rc6 in sysfs functions conditional

Unfortunately Hunt didn't respond to my review comments, and Daniel
sucked in the patch again ignoring. Worst of all, I'm too lazy to write
the patch for what I originally wanted, which was to keep rc6 sysfs even
without CONFIG_PM. This simpler patch does enough to enable us to add
more sysfs entries though.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>