drm/i915: Add new CNL PCH ID seen on a CML platform

Atm we don't detect a PCH with PCI ID 0xA3C1 which showed up now on a CML
platform. We don't have the official assignment of the PCH PCI IDs, but
this looks like a CNP which was already used on CML platforms. Let's add
the new ID->PCH type mapping accordingly.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112051
Reported-and-tested-by: Cyrus <cyrus.lien@canonical.com>
Cc: Cyrus <cyrus.lien@canonical.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191022095155.30991-1-imre.deak@intel.com