drm/i915: Unbind objects in shrinker only if device is runtime active

drm/i915: Unbind objects in shrinker only if device is runtime active

When the system is running low on memory, gem shrinker is invoked.
In this process objects will be unbounded from GTT and unbinding process
will require access to GTT(GTTADR) and also to fence register potentially.
That requires a resume of gfx device, if suspended, in the shrinker path.
Considering the power leakage due to intermediate resume, perform unbinding
operation only if device is already runtime active.

v2: Use newly implemented intel_runtime_pm_get_if_in_use (Chris)

Signed-off-by: Akash Goel <akash.goel@intel.com>
Signed-off-by: Praveen Paneri <praveen.paneri@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1462178429-13449-1-git-send-email-praveen.paneri@intel.com
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>