drm/i915/gen11: Start distinguishing 'phy' from 'port'

Our past DDI-based Intel platforms have had a fixed DDI<->PHY mapping.
Because of this, both the bspec documentation and our i915 code has used
the term "port" when talking about either DDI's or PHY's; it was always
easy to tell what terms like "Port A" were referring to from the
context.

Unfortunately this is starting to break down now that EHL allows PHY-A
to be driven by either DDI-A or DDI-D.  Is a setup with DDI-D driving
PHY-A considered "Port A" or "Port D?"  The answer depends on which
register we're working with, and even the bspec doesn't do a great job
of clarifying this.

Let's try to be more explicit about whether we're talking about the DDI
or the PHY on gen11+ by using 'port' to refer to the DDI and creating a
new 'enum phy' namespace to refer to the PHY in use.

This patch just adds the new PHY namespace, new phy-based versions of
intel_port_is_*(), and a helper to convert a port to a PHY.
Transitioning various areas of the code over to using the PHY namespace
will be done in subsequent patches to make review easier.  We'll remove
the intel_port_is_*() functions at the end of the series when we
transition all callers over to using the PHY-based versions.

v2:
 - Convert a few more 'port' uses to 'phy.' (Sparse)

v3:
 - Switch DDI_CLK_SEL() back to 'port.' (Jose)
 - Add a code comment clarifying why DPCLKA_CFGCR0_ICL needs to use PHY
   for its bit definitions, even though the register description is
   given in terms of DDI.
 - To avoid confusion, switch CNL's DPCLKA_CFGCR0 defines back to using
   port and create separate ICL+ definitions that work in terms of PHY.

v4:
 - Rebase and resolve conflicts with Imre's TC series.
 - This patch now just adds the namespace and a few convenience
   functions; the important changes are now split out into separate
   patches to make review easier.

Suggested-by: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190709183934.445-2-matthew.d.roper@intel.com