drm/i915/icl: store the port type for TC ports

The type is detected based on the live status bits. Once detected,
it's not supposed to be changed, so we have some sanity checks for
that.

v2: Rebase.

Cc: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180725002813.6938-3-paulo.r.zanoni@intel.com