drm/i915/icl: Show interrupt registers in debugfs

Show GEN11 specific interrupt registers in debugfs

v2: Update for POR changes. (Daniele Ceraolo Spurio)
v3: get runtime pm ref. unify common parts with gen8 (Daniele)

Cc: Ceraolo Spurio, Daniele <daniele.ceraolospurio@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180220153755.13509-2-mika.kuoppala@linux.intel.com