Add debug macros

- Add 'debug.h' with INFO, WARN and ERROR macros.
- This prints the specified message with the appropriate tag.
- INFO and WARN messages are only displayed when building with
  the DEBUG flag set. Error messages are always printed.

Change-Id: I21835b6063fcc99649b30ac7489387cbd3705bc0

include/debug.h

+/*
+ * Copyright (c) 2013, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __DEBUG_H__
+#define __DEBUG_H__
+
+/* Do not try to call this from ASM code. */
+#ifndef __ASSEMBLY__
+
+#include <stdio.h>
+
+/* If building the project with DEBUG disabled the INFO and WARN macros
+ * won't produce any output. The ERROR macro is always enabled.
+ * The format expected is the same as for printf().
+ * INFO("Info %s.\n", "message")    -> INFO: Info message.
+ * WARN("Warning %s.\n", "message") -> WARN: Warning message.
+ * ERROR("Error %s.\n", "message")  -> ERROR: Error message.
+ *
+ * TODO : add debug levels.
+ */
+#if DEBUG
+ #define INFO(...)	printf("INFO: " __VA_ARGS__)
+ #define WARN(...)	printf("WARN: " __VA_ARGS__)
+#else
+ #define INFO(...)
+ #define WARN(...)
+#endif
+
+#define ERROR(...)	printf("ERROR: " __VA_ARGS__)
+
+#endif /* __ASSEMBLY__ */
+#endif /* __DEBUG_H__ */