Simplify runtime version info string methods

Return a const char* instead of taking a char* as an argument.

This aligns us with the interface used in TF PSA Crypto.

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
diff --git a/ChangeLog.d/runtime-version-interface.txt b/ChangeLog.d/runtime-version-interface.txt
new file mode 100644
index 0000000..1cf4266
--- /dev/null
+++ b/ChangeLog.d/runtime-version-interface.txt
@@ -0,0 +1,9 @@
+API changes
+   * Change the signature of the runtime version information methods that took
+     a char* as an argument to take zero arguments and return a const char*
+     instead. This aligns us with the interface used in TF PSA Crypto 1.0.
+     If you need to support linking against both Mbed TLS 3.x and 4.x, please
+     use the build-time version macros or mbedtls_version_get_number() to
+     determine the correct signature for mbedtls_version_get_string() and
+     mbedtls_version_get_string_full() before calling them.
+     Fixes issue #10308.