pwm: Do stricter return value checking for .round_waveform_tohw()

pwm: Do stricter return value checking for .round_waveform_tohw()

The .round_waveform_tohw() is supposed to return 0 if the request could
be rounded down to match the hardware capabilities and return 1 if
rounding down wasn't possible.

Expand the PWM_DEBUG check to not only assert proper downrounding if 0
was returned but also check that it was actually rounded up when the
callback signalled uprounding.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://lore.kernel.org/r/dfb824ae37f99df068c752d48cbd163c044a74fb.1743844730.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>