dt-bindings: pwm: at91: Add sam9x7 compatible strings list

Add compatible strings list for SAM9X7.

Signed-off-by: Varshini Rajendran <varshini.rajendran@microchip.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240223172619.672262-1-varshini.rajendran@microchip.com


Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>