drm/i915/gt: runtime-pm is no longer required for ce->ops->pin()

Now that we have moved the runtime-pm management out of
intel_context_acctive_acquire, and that itself out of ce->ops->pin(), no
explicit runtime pm wakeref is required in intel_context_pin().

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200109085717.873326-3-chris@chris-wilson.co.uk