reset: sti: rely on regmap_field_read_poll_timeout for ack wait

Use regmap_field_read_poll_timeout function when waiting for the
ack bit upon performing the reset control.

Signed-off-by: Alain Volmat <avolmat@me.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/20230210224332.98482-1-avolmat@me.com


Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>