Get rid of several platform specific variants of
intel_digital_port_connected() and just use the ISR bits we've
stashed away.

v2: Duplicate stuff to avoid exposing platform specific
    functions across files (Jani)
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200311155422.3043-4-ville.syrjala@linux.intel.comReviewed-by: NImre Deak <imre.deak@intel.com>