drm/i915: Move the TypeC port handling code to a separate file

Move the TypeC port handling functions to a new file for clarity.

While at it:
- s/icl_tc_port_connected()/intel_tc_port_connected()/
  icl_tc_phy_disconnect(), will be unexported later.

- s/intel_dp_get_fia_supported_lane_count()/
    intel_tc_port_fia_max_lane_count()/
  It's used for HDMI legacy mode too.

- Simplify function interfaces by passing only dig_port to them.

No functional changes.

v2:
- Fix checkpatch issues: +1/-1 empty lines in intel_tc.c and add
  missing SPDX to intel_tc.h. (Jani)

Cc: Animesh Manna <animesh.manna@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190628143635.22066-4-imre.deak@intel.com