imx9: soc: imx9: soc: Align UID endianness with ROM

imx9: soc: imx9: soc: Align UID endianness with ROM

ROM use UID[0] and UID[1] as serial number with big endian when usb serial
download.

After update this, uuu(>1.6) can use below command to filter out devices
when multi boards connected.

uuu -ms <serial#> ...

[sudo] uuu -lsusb can list known devices with serial# informaiton.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>