drm/i915/skl: Adding power domains for AUX controllers

Adding new power doamins for AUX controllers

v2: Added new power domains in power_domain_str per Imre's comment

v3: Added AUX power domains to older platforms

v4: Rebase on top of POWER_DOMAIN_PLLS.

v5: Modified to address review comments from Imre

Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Satheeshakrishna M <satheeshakrishna.m@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com> (v3)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>