drm/i915/ehl: Define EHL powerwells independently of ICL

Outputs C and D on EHL are combo PHY outputs and thus should not be
using the same TC AUX power well handlers as ICL.  And even though
icl_combo_phy_aux_power_well_ops works okay for EHL/JSL combo PHYs none
of its special handling is actually necessary for this platform:
 * EHL/JSL don't actually need to program PORT_CL_DW12
 * Display WA #1178 does not apply to EHL/JSL

Thus we can simply drop back to using our standard "hsw-style" power
well ops for EHL AUX power wells.

Bspec: 4301
Fixes: f722b8c1

 ("drm/i915/ehl: All EHL ports are combo phys")
Cc: Jose Souza <jose.souza@intel.com>
Cc: Bob Paauwe <bob.j.paauwe@intel.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191213001511.678070-2-matthew.d.roper@intel.com
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>