The TypeC port mode can switch dynamically, to reflect that better call
the port's mode as 'mode' rather than 'type'.

While at it:
- s/TC_PORT_TBT/TC_PORT_TBT_ALT/ and s/TC_PORT_TYPEC/TC_PORT_DP_ALT/.
  'TYPEC' is ambiguous, TBT_ALT and DP_ALT better match the reality.

- Remove the 'unknown' TypeC port mode. The mode is always known, it's
  the TBT-alt/safe mode after HW reset and after disconnecting the PHY.
  Simplify the tc_port/tc_type checks accordingly.

- Don't WARN if the port mode changes, that can happen normally.

No functional changes.

Cc: Animesh Manna <animesh.manna@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@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: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190628143635.22066-5-imre.deak@intel.com