pwm: stm32: Use regmap_clear_bits and regmap_set_bits where applicable

Found using coccinelle and the following semantic patch:

@@
expression map, reg, bits;
@@

- regmap_update_bits(map, reg, bits, bits)
+ regmap_set_bits(map, reg, bits)

@@
expression map, reg, bits;
@@

- regmap_update_bits(map, reg, bits, 0)
+ regmap_clear_bits(map, reg, bits)

Tested-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20221115111347.3705732-6-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>