drm: tda99x: Don't advertise non-existent capture support

As far as I can tell none of the tda998x devices support audio capture so
don't advertise support for it, ensuring that we don't confuse userspace.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/20221130184644.464820-3-broonie@kernel.org


Signed-off-by: Mark Brown <broonie@kernel.org>