drm/i915: Pass the level to intel_prepare_hdmi_ddi_buffers()

The caller of intel_prepare_hdmi_ddi_buffers() alreday figured out the
level, so let's just pass it in instead if figuring it out again.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171016145705.11780-5-ville.syrjala@linux.intel.com


Reviewed-by: James Ausmus <james.ausmus@intel.com>