drivers: firmware: scmi: add cpu lpm interface api

Added scmi_cpu_pd_lpm_set api for nxp imx scmi interface

This api set the lpm setting for some peripherals applied
when cpu enter a low power mode, such as keep iMX95 wakeup mix
power on when M7 core enter suspend mode, scmi agent record and
deal with this request

Signed-off-by: Yongxu Wang <yongxu.wang@nxp.com>