drm/i915/ehl: Map MCC pins based on PHY, not port

Now that we distinguish between phy and port(ddi), mcc_port_to_ddc_pin
should use the phy, not the DDI, for determining DDC pins.

We're only converting the MCC function at the moment since EHL is the
only platform that has configurations where port!=phy.

Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190712221641.21031-1-matthew.d.roper@intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>