arm64: dts: ti: k3-am625-sk: Add ECAP APWM nodes

AM62 has 3 ECAP instances with 1 APWM each. Add DT nodes for the same.
Keep them disabled in am625-sk dts as these pins can be repurposed in
user exp connector.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Aswath Govindraju <a-govindraju@ti.com>
Link: https://lore.kernel.org/r/20220419062902.196526-1-vigneshr@ti.com