arm64: dts: ti: k3-am64-main: add main CPTS entry

Add DT node for the Main domain CPTS.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210304211038.12511-3-grygorii.strashko@ti.com