ASoC: rt5645: Refactor rt5645_parse_dt()

Refactor rt5645_parse_dt(), make it take a pointer to
struct rt5645_platform_data as argument instead of passing in
the complete rt5645_priv struct.

While at it also make it void since it always succeeds.

This is a preparation patch for factoring the code to get
the platform-data out into a separate helper function.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://msgid.link/r/20231126214024.300505-4-hdegoede@redhat.com
Signed-off-by: Mark Brown <broonie@kernel.org>