tf-m: Update the document by adding missing sections

These additions are mainly inherited from this document:
`https://git.gitlab.arm.com/iot/open-iot-sdk/sdk/-/blob/


main/components/trusted-firmware-m/README.md`. However,
some modifications were made to match the FRI's project
use case.

Signed-off-by: Ahmed Ismail <Ahmed.Ismail@arm.com>