arm64: dts: ti: k3-am64-main: Add epwm nodes

Add DT nodes for all epwm instances present in AM64 SoC.

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/20210721113625.17299-2-lokeshvutla@ti.com