[zep fromtree] LIB: Add tfm_vprintf_unpriv

Add the implementation of vprintf for unprivileged logging. This
function follows the same signature as the standard library vprintf.

Change-Id: I512e1835c0c93e72be46f06508c1b66d67587dbf
Signed-off-by: Jackson Cooper-Driver <jackson.cooper-driver@arm.com>
(cherry picked from commit 4d5ce0e)

Author: jackson-cooperd

lib/tfm_log_unpriv/inc/tfm_vprintf_unpriv.h

@@ -0,0 +1,15 @@
+/*
+ * SPDX-FileCopyrightText: Copyright The TrustedFirmware-M Contributors
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#ifndef __TFM_VPRINTF_UNPRIV_H__
+#define __TFM_VPRINTF_UNPRIV_H__
+
+#include <stdarg.h>
+
+void tfm_vprintf_unpriv(const char *fmt, va_list args);
+
+#endif /* __TFM_VPRINTF_UNPRIV_H__ */

lib/tfm_log_unpriv/src/tfm_log_unpriv.c

@@ -46,16 +46,22 @@ static void output_string_to_buf(void *priv, const char *str, uint32_t len)
     data->buf_pos += len;
 }
 
-void tfm_log_unpriv(const char *fmt, ...)
+void tfm_vprintf_unpriv(const char *fmt, va_list args)
 {
-    va_list args;
     struct tfm_log_unpriv_data data;
 
     data.buf_pos = 0;
 
-    va_start(args, fmt);
     tfm_vprintf(output_string_to_buf, &data, fmt, args);
-    va_end(args);
 
     output_buf(data.buf, data.buf_pos);
 }
+
+void tfm_log_unpriv(const char *fmt, ...)
+{
+    va_list args;
+
+    va_start(args, fmt);
+    tfm_vprintf_unpriv(fmt, args);
+    va_end(args);
+}