pwm: Fix incorrect variable used in error message

pwm: Fix incorrect variable used in error message

The dev_err message is reporting the incorrect return value ret_tohw,
it should be reporting the value in ret_fromhw. Fix this by using
ret_fromhw instead of ret_tohw.

Fixes: 6c5126c6406d ("pwm: Provide new consumer API functions for waveforms")
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20250902130348.2630053-1-colin.i.king@gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>