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/marvell/a3700/common/include/io_addr_dec.h b/plat/marvell/a3700/common/include/io_addr_dec.h
index 79f6f2c..42ef30b 100644
--- a/plat/marvell/a3700/common/include/io_addr_dec.h
+++ b/plat/marvell/a3700/common/include/io_addr_dec.h
@@ -5,8 +5,8 @@
  * https://spdx.org/licenses
  */
 
-#ifndef _IO_ADDR_DEC_H_
-#define _IO_ADDR_DEC_H_
+#ifndef IO_ADDR_DEC_H
+#define IO_ADDR_DEC_H
 
 #include <stdint.h>
 
@@ -63,5 +63,4 @@
 		     struct dec_win_config *io_dec_config,
 		     uint32_t io_unit_num);
 
-#endif /* _IO_ADDR_DEC_H_ */
-
+#endif /* IO_ADDR_DEC_H */