pwm: stm32: Fix complementary output in round_waveform_tohw()

When the timer supports complementary output, the CCxNE bit must be set
additionally to the CCxE bit. So to not overwrite the latter use |=
instead of = to set the former.

Fixes: deaba9cf ("pwm: stm32: Implementation of the waveform callbacks")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20241217150021.2030213-1-fabrice.gasnier@foss.st.com


[ukleinek: Slightly improve commit log]
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>