Again we wish to operate on the engines, which are owned by the
intel_gt. As such it is easier, and much more consistent, to pass the
intel_gt parameter.

v2: Unexport i915_gem_load_power_context()

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191022141935.15733-1-chris@chris-wilson.co.uk