DRM / i915: Fix resume regression on MSI Wind U100 w/o KMS

DRM / i915: Fix resume regression on MSI Wind U100 w/o KMS

Commit cbda12d77ea590082edb6d30bd342a67ebc459e0 (drm/i915: implement
new pm ops for i915), among other things, removed the .suspend and
.resume pointers from the struct drm_driver object in i915_drv.c,
which broke resume without KMS on my MSI Wind U100.

Fix this by reverting that part of commit cbda12d77ea59.

[ The DRM layer will not use the class-specific suspend/resume functions
  if the driver is marked MODESET-aware, and conversely it will not
  register the PCI device if the drievr isn't so marked, so you always
  end up with _either_ the drm-class suspend/resume _or_ the PCI layer
  PM functionality, never both.  - Linus ]

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>