drm/i915/cnl: Add HPD support for Port F.

drm/i915/cnl: Add HPD support for Port F.

On CNP boards that are using DDI F,
bit 25 (SDE_PORTE_HOTPLUG_SPT) is representing
the Digital Port F hotplug line when the Digital
Port F hotplug detect input is enabled.

v2: Reuse all existent structure instead of adding a
new HPD_PORT_F pointing to pin of port E.
v3: Use IS_CNL_WITH_PORT_F so we can start upstreaming
    this right now. If that SKU ever get a proper name
    we come back and update it.
v4: Rebase on top of digital connected port using encoder
    instead of port.
v5: Moved IS_CNL_WITH_PORT_F definition to the PCI IDs patch.

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180129232223.766-8-rodrigo.vivi@intel.com