implement loader API according to HAL design.
Description
Event Timeline
use different 'inc' file and int function for different models.
https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/4629/1
move spm header files to spm folder:
https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/4630/3
Use separate source for different models:
https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/5101
Fix platform HAL return type:
https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/5160
Use separate head file for two models:
https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/5102
Separate SPM data structure definition:
https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/5187
Align partition structure with HAL:
https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/5050