spi: rzv2h-rspi: use device-managed APIs

spi: rzv2h-rspi: use device-managed APIs

Non-device-managed APIs were initially used here to avoid the buggy
interaction between PM domains and device-managed actions.

Commit f99508074e78 ("PM: domains: Detach on device_unbind_cleanup()")
fixed the interaction between PM domains and device-managed actions.

Simplify the code by using device-managed actions to unregister the SPI
controller and to assert and release the resets.

Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Link: https://patch.msgid.link/20251201134229.600817-5-cosmin-gabriel.tanislav.xa@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>