drm/i915: remove excessive i915_gem_drain_freed_objects

i915_gem_drain_workqueue() call i915_gem_drain_freed_objects()
so no need to call that again.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220923073515.23093-2-nirmoy.das@intel.com