drm/i915/icl: Add DDI HDMI level selection for ICL

This patch adds a proper HDMI DDI entry level for vswing
programming sequences on ICL.

Spec doesn't specify any default for HDMI tables,
so let's pick the last entry as the default for now
to stay consistent with older platform like CNL.

Cc: Rakshmi Bhatia <rakshmi.bhatia@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180522002558.29262-8-paulo.r.zanoni@intel.com