Disconnecting the TypeC PHY when the port is in legacy mode is not
necessary:
- BSpec doesn't specify a disconnect sequence for legacy mode.
- The use of the PHY is dedicated for the display in legacy mode.
- We keep the PHY always connected during runtime as well in legacy
  mode.

We disconnect the PHY when needed during a disabling modeset for the
port, so we can also remove the disconnect call from the destroy hook.

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/20190628143635.22066-23-imre.deak@intel.com