On Icelake platform, MG PHY is used when operating in DP alternate
mode or the legacy HDMI or DP modes. DDI Ports C, D, E, F are MG PHY
DDI ports on ICL.

This patch adds the necessary voltage swing programming related
register definitions and macros for MG PHY DDI ports.

v4 (from Paulo):
* Use _PORT instead of _PICK
* Change some mask names to our current coding standards
* Stay under 80 columns
v3:
* Rebase on new revision of patches
v2:
* Remove whitespaces in the #defines (Paulo)

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NManasi Navare <manasi.d.navare@intel.com>
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180323172419.24911-4-paulo.r.zanoni@intel.com