drm/vc4: hdmi: Remove unused argument in vc4_hdmi_supports_scrambling

Even though vc4_hdmi_supports_scrambling takes a mode as an argument, it
never uses it. Let's remove it.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220829134731.213478-3-maxime@cerno.tech