arm: dts: k3-j721e-r5-common-proc-board: tps659413: Correct the min/max voltages of VDD_CPU

Correct the min/max voltages of VDD_CPU. As per data sheet the VDD_CPU
minimum voltage is .6V & maximum voltage is .9V.

Correct the same. While at it fix the comment to reflect VDD_CPU
instead of VDD_MPU.

Data Sheet Link: https://www.ti.com/lit/gpn/dra829v



Signed-off-by: Keerthy <j-keerthy@ti.com>