Relative submodule URLs are resolved against the remote URL of the
superproject, so a mirror or an internal fork of this repository picks
up sibling mirrors of mbedtls-framework and TF-PSA-Crypto on its own,
without having to patch .gitmodules in every copy.
Resolution against the upstream remote is unchanged:
https://github.com/Mbed-TLS/mbedtls.git + ../mbedtls-framework
-> https://github.com/Mbed-TLS/mbedtls-frameworkhttps://github.com/Mbed-TLS/mbedtls.git + ../TF-PSA-Crypto.git
-> https://github.com/Mbed-TLS/TF-PSA-Crypto.git
The same holds for SSH and scp-like remotes, so ordinary clones of
Mbed-TLS/mbedtls behave exactly as before.
Signed-off-by: Parminder Singh <parminder.sh93@gmail.com>