arm: dts: k3-j7200-r5-common: fix the mcu_timer0 clock frequency

Correcting the clock-frequency property of the mcu_timer0 node

Fixes: df73e791 ("arm: dts: j7200: dts sync with Linux 6.6-rc1")
Signed-off-by: Aniket Limaye <a-limaye@ti.com>
Reviewed-by: Udit Kumar <u-kumar1@ti.com>