video: hdmi: Remove unused hdmi_infoframe_check

hdmi_infoframe_check() has been unused since it was added in
commit c5e69ab3 ("video/hdmi: Constify infoframe passed to the pack
functions")

Remove it.

Note that the individual check functions for each type are
actually used, so they're staying.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Helge Deller <deller@gmx.de>