drm/i915: Force a TypeC PHY disconnect during suspend/shutdown

Disconnect TypeC PHYs during system suspend and shutdown, even with the
corresponding TypeC sink still plugged to its connector, since leaving
the PHY connected causes havoc at least during system resume in the
presence of an Nvidia card.

Note that this will only make a difference in the TypeC DP alternate
mode, since in Thunderbolt alternate mode the PHY is never owned by the
display engine and there is no notion of PHY ownership in legacy mode
(the display engine being the only possible owner in that mode and the
TypeC subsystem not having anything to do with the port in that case).

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3500
Reported-and-tested-by: Chris Chiu <chris.chiu@canonical.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210610174223.605904-1-imre.deak@intel.com