imx9: Add i.MX94 CPU type and SoC-level Kconfig

imx9: Add i.MX94 CPU type and SoC-level Kconfig

Introduce support for the new i.MX94 processor, including its CPU type
and SoC-level Kconfig entry.

The i.MX94 is a new member of the i.MX9 family. It uses a System Manager
to handle system-level functions such as power, clock, sensor and pin
control. The System Manager runs on a Cortex-M processor, while the
Cortex-A processor communicates with it via the ARM SCMI protocol and a
messaging unit.

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Alice Guo <alice.guo@nxp.com>
Acked-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Jacky Bai <ping.bai@nxp.com>