drm/i915: Mark up ips for RCU protection

drivers/gpu/drm/i915/intel_pm.c:8352:9: error: incompatible types in comparison expression (different address spaces)
drivers/gpu/drm/i915/intel_pm.c:8359:9: error: incompatible types in comparison expression (different address spaces)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190412085410.10392-3-chris@chris-wilson.co.uk