feat(build): add Mbed TLS submodule

This change adds Mbed TLS 3.6.5 as a submodule to the TF-A repository.
It is no longer a requirement to pass `MBEDTLS_DIR` to the build system
when building confi

feat(build): add Mbed TLS submodule

This change adds Mbed TLS 3.6.5 as a submodule to the TF-A repository.
It is no longer a requirement to pass `MBEDTLS_DIR` to the build system
when building configurations which require it, as the build system will
now look inside the `contrib` directory if the parameter is missing.

If you cloned TF-A without the `--recurse-submodules` flag, you can
ensure that this submodule is present by running:

git submodule update --init --recursive

BREAKING-CHANGE: Mbed TLS is now included in the TF-A repository, and it
is no longer a requirement to pass `MBEDTLS_DIR` to the build system.
Please run `git submodule update --init --recursive` if you encounter
issues after migrating to the latest version of TF-A.

Change-Id: Iad777e77936d1c373065f17fe5c4aadc45e56b64
Signed-off-by: Chris Kay <chris.kay@arm.com>

show more ...