The 'marvell,pwm-offset' property of both GPIO blocks (per CP component)
point to the same counter registers offset. The driver will decide how
to use counters A/B.

This is different from the convention of pwm on earlier Armada series
(370/38x). On those systems the assignment of A/B counters to GPIO
blocks is coded in both DT and the driver. The actual behaviour of the
current driver on Armada 8K/7K is the same as earlier systems.

Add also clock properties for base pwm frequency reference.
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>