drm/edid: add helper for HDMI VSDB audio latency field length

Add a helper for skipping the HDMI VSDB audio latency fields.

There's a functional change for HDMI VSDB blocks that do not respect the
spec: "I_Latency_Fields_Present shall be zero if Latency_Fields_Present
is zero". We assume this to hold when skipping the latency fields, and
ignore non-zero I_Latency_Fields_Present if Latency_Fields_Present is
zero.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/da4293203ef2ddeb0bf66a2bfdbc129ab609c543.1672826282.git.jani.nikula@intel.com