arm64: dts: ti: k3-am642-sk: Add pwm nodes

ecap0 can be configured to use pad ECAP0_IN_APWM_OUT (D18) which has a
signal connected to Pin 1 of J3. Add support for adding this pinmux so
that pwm can be observed on pin 1 of Header J3

Also mark all un-used epwm and ecap pwm nodes as disabled.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Link: https://lore.kernel.org/r/20210721113625.17299-5-lokeshvutla@ti.com