ASoC: rt5645: Add rt5645_get_pdata() helper

Add a rt5645_get_pdata() helper function which retreives the platform-data
and overrides it with the quirks module parameter if that is set.

This is a preparation patch for adding the rt5645_components() function.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://msgid.link/r/20231126214024.300505-5-hdegoede@redhat.com
Signed-off-by: Mark Brown <broonie@kernel.org>