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/mediatek/mt8173/include/power_tracer.h b/plat/mediatek/mt8173/include/power_tracer.h
index e8c0552..195366d 100644
--- a/plat/mediatek/mt8173/include/power_tracer.h
+++ b/plat/mediatek/mt8173/include/power_tracer.h
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#ifndef __POWER_TRACER_H__
-#define __POWER_TRACER_H__
+#ifndef POWER_TRACER_H
+#define POWER_TRACER_H
 
 #define CPU_UP		0
 #define CPU_DOWN	1
@@ -16,4 +16,4 @@
 
 void trace_power_flow(unsigned long mpidr, unsigned char mode);
 
-#endif
+#endif /* POWER_TRACER_H */