drm/i915/icl: Fix combo PHY uninit

BSpec says to clear the comp init HW flag too during combo PHY uninit,
so do that. The lack of this could badly interact with the PHY reinit
after a DC6/9 transition at least, where (after a follow-up patch fixing
the init code) we'd skip the initialization incorrectly due to this flag
being set.

BSpec: 21257
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181106160621.23057-2-imre.deak@intel.com