Adjust build systems

Adjust build systems such as we can built
Mbed TLS in the default and full configuration.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/tf-psa-crypto/drivers/CMakeLists.txt b/tf-psa-crypto/drivers/CMakeLists.txt
new file mode 100644
index 0000000..f03055e
--- /dev/null
+++ b/tf-psa-crypto/drivers/CMakeLists.txt
@@ -0,0 +1 @@
+add_subdirectory(builtin)