[TF-A] Suspend to RAM support for K3 J7200

Hello,

I just sent a series to gerrit: https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/23992. I'm writing this email to add more context to this series, as I didn't find how to to it with gerrit.

This series is only the TF-A part to add suspend to RAM support for the TI K3 J7200 target. Some modifications are also needed in Linux kernel, U-Boot (R5 SPL) and DM-Firmware. During the suspend sequence, TF-A save itself in DRAM, in a reserved memory region dedicated to lpm. TF-A will be restored by R5 SPL. We need to save it in DRAM (which will be in retention mode during suspend) because as it runs in SRAM, it will be lost once the SOC is powered-off by the PMIC.

Best Regards,