Standardise header guards across codebase

All identifiers, regardless of use, that start with two underscores are
reserved. This means they can't be used in header guards.

The style that this project is now to use the full name of the file in
capital letters followed by 'H'. For example, for a file called
"uart_example.h", the header guard is UART_EXAMPLE_H.

The exceptions are files that are imported from other projects:

- CryptoCell driver
- dt-bindings folders
- zlib headers

Change-Id: I50561bf6c88b491ec440d0c8385c74650f3c106e
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/plat/nvidia/tegra/include/drivers/mce.h b/plat/nvidia/tegra/include/drivers/mce.h
index c7867a5..8140870 100644
--- a/plat/nvidia/tegra/include/drivers/mce.h
+++ b/plat/nvidia/tegra/include/drivers/mce.h
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#ifndef __MCE_H__
-#define __MCE_H__
+#ifndef MCE_H
+#define MCE_H
 
 #include <mmio.h>
 #include <tegra_def.h>
@@ -73,4 +73,4 @@
 void mce_update_cstate_info(const mce_cstate_info_t *cstate);
 void mce_verify_firmware_version(void);
 
-#endif /* __MCE_H__ */
+#endif /* MCE_H */