pwm: hibvt: Use individual struct per of-data

Split pwm_soc array in one struct per SoC and point to the corresponding
one in of-data.

Signed-off-by: Mathieu Othacehe <m.othacehe@gmail.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>