Move MBEDTLS_USE_PSA_CRYPTO to "Builtin drivers" section

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/docs/proposed/config-split.md b/docs/proposed/config-split.md
index 69a45b8..148b6a6 100644
--- a/docs/proposed/config-split.md
+++ b/docs/proposed/config-split.md
@@ -285,6 +285,7 @@
 //#define MBEDTLS_SHA512_SMALLER
 //#define MBEDTLS_SHA512_USE_A64_CRYPTO_IF_PRESENT
 //#define MBEDTLS_SHA512_USE_A64_CRYPTO_ONLY
+//#define MBEDTLS_USE_PSA_CRYPTO
 
 //#define MBEDTLS_ECP_FIXED_POINT_OPTIM      1
 //#define MBEDTLS_ECP_WINDOW_SIZE            4
@@ -462,7 +463,6 @@
 #define MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_ENABLED
 #define MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL_ENABLED
 //#define MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH
-//#define MBEDTLS_USE_PSA_CRYPTO
 #define MBEDTLS_VERSION_C
 #define MBEDTLS_VERSION_FEATURES
 //#define MBEDTLS_X509_REMOVE_INFO