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/pmc.h b/plat/nvidia/tegra/include/drivers/pmc.h
index ea9392b..14c9225 100644
--- a/plat/nvidia/tegra/include/drivers/pmc.h
+++ b/plat/nvidia/tegra/include/drivers/pmc.h
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#ifndef __PMC_H__
-#define __PMC_H__
+#ifndef PMC_H
+#define PMC_H
 
 #include <mmio.h>
 #include <tegra_def.h>
@@ -40,4 +40,4 @@
 void tegra_pmc_cpu_on(int32_t cpu);
 __dead2 void tegra_pmc_system_reset(void);
 
-#endif /* __PMC_H__ */
+#endif /* PMC_H */