drm/i915/display: remove strap checks from gen 9

Direction on gen9+ was to stop reading the straps and only rely on the
VBT for marking the port presence. This happened while dealing with
WaIgnoreDDIAStrap and instead of using it as a WA, it should now be the
normal flow. See commit 885d3e5b

 ("drm/i915/display: fix comment on
skl straps").

For gen 10 it's hard to say if this will work or not since I can't test
it, so leave it with the same behavior as before.

For PCH_TGP we should still rely on the VBT to make ports E and F not
available.

v2 (Ville):
  - use display ver >= 9 to make it consistent with the rest of the
    driver instead of checking for == 9
  - also handle CNL and only initialize port F if it is
    IS_CNL_WITH_PORT_F. Eventually CNL may be removed, but while it
    isn't let's keep it consistent everywhere

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210430223808.1078010-4-lucas.demarchi@intel.com