tls: Remove duplicate psa_util.h include

Don't include psa_util.h twice. It's enough to include it once.
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 68a1e59..d04fa9b 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -59,10 +59,6 @@
 #include "mbedtls/oid.h"
 #endif
 
-#if defined(MBEDTLS_USE_PSA_CRYPTO)
-#include "mbedtls/psa_util.h"
-#endif
-
 static void ssl_reset_in_out_pointers( mbedtls_ssl_context *ssl );
 static uint32_t ssl_get_hs_total_len( mbedtls_ssl_context const *ssl );