Unfortunately, we had two files named oid.h - one in the main repo, and one in the tf-psa-crypto repo, and these files included the mbedtls one, so I restored the header include

Signed-off-by: Anton Matkin <anton.matkin@arm.com>
diff --git a/tests/suites/test_suite_x509write.function b/tests/suites/test_suite_x509write.function
index 0c0e799..40677f2 100644
--- a/tests/suites/test_suite_x509write.function
+++ b/tests/suites/test_suite_x509write.function
@@ -4,7 +4,7 @@
 #include "mbedtls/x509_csr.h"
 #include "x509_internal.h"
 #include "mbedtls/pem.h"
-#include "mbedtls/private/oid.h"
+#include "mbedtls/oid.h"
 #include "x509_oid.h"
 #include "mbedtls/private/rsa.h"
 #include "mbedtls/asn1.h"