Baremetal config: Remove deprecated functions

This doesn't make a difference after link time optimization
because they aren't used, but it yields more accurate code-size
figures from baremetal.sh.
diff --git a/configs/baremetal.h b/configs/baremetal.h
index f8ad61c..0977732 100644
--- a/configs/baremetal.h
+++ b/configs/baremetal.h
@@ -149,6 +149,8 @@
 /* Server-side only */
 #define MBEDTLS_SSL_SRV_C
 
+#define MBEDTLS_DEPRECATED_REMOVED
+
 #if defined(MBEDTLS_USER_CONFIG_FILE)
 #include MBEDTLS_USER_CONFIG_FILE
 #endif