arm64: dts: ti: k3-j721s2: disable "mcu_cpsw" in SoC file and enable in board files

arm64: dts: ti: k3-j721s2: disable "mcu_cpsw" in SoC file and enable in board files

Following the existing convention of disabling nodes in the SoC file and
enabling only the required ones in the board file, disable "mcu_cpsw" node
in the SoC file "k3-j721s2-mcu-wakeup.dtsi" and enable it in the board
files:
a) k3-am68-phyboard-izar.dts
b) k3-am68-sk-base-board.dts
c) k3-j721s2-common-proc-board.dts

Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Link: https://patch.msgid.link/20251015111344.3639415-6-s-vadapalli@ti.com
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>