soc: nxp: add SoC imx91 support

The i.MX 91 SoC’s integrated EdgeLock® Secure Enclave provides
security features including lifecycle management, tamper detection,
secure boot and a simplified path to certifications. The i.MX 91
family features an Arm® Cortex®-A55 running at up to 1.4GHz,
support for modern LPDDR4 memory to enable platform longevity,
dual Gigabit Ethernet and dual USB ports, along with a rich set
of peripherals targeting medical, industrial and consumer IoT
market segments.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>