drm/i915/sdvo: Don't write stack garbage into the hbuf

Pass the length returned by hdmi_infoframe_pack_only() to
intel_sdvo_write_infoframe() so that we don't end up writing
stack garbage into the hbuf.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190409144054.24561-7-ville.syrjala@linux.intel.com


Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>