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/rockchip/rk3399/drivers/dram/dfs.h b/plat/rockchip/rk3399/drivers/dram/dfs.h
index e847b2e..172b2a7 100644
--- a/plat/rockchip/rk3399/drivers/dram/dfs.h
+++ b/plat/rockchip/rk3399/drivers/dram/dfs.h
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#ifndef __SOC_ROCKCHIP_RK3399_DFS_H__
-#define __SOC_ROCKCHIP_RK3399_DFS_H__
+#ifndef DFS_H
+#define DFS_H
 
 #include <stdint.h>
 
@@ -47,4 +47,4 @@
 void ddr_prepare_for_sys_suspend(void);
 void ddr_prepare_for_sys_resume(void);
 
-#endif
+#endif /* DFS_H */