arm: mach-k3: am62a: Add main_timer0 id to the dev list

main_timer0 is used by u-boot as the tick-timer. Add it to the soc
devices list so it an be enabled via the k3 power controller.

Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Neha Malcom Francis <n-francis@ti.com>