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/ti/k3/common/drivers/sec_proxy/sec_proxy.h b/plat/ti/k3/common/drivers/sec_proxy/sec_proxy.h
index facfd19..2d987f8 100644
--- a/plat/ti/k3/common/drivers/sec_proxy/sec_proxy.h
+++ b/plat/ti/k3/common/drivers/sec_proxy/sec_proxy.h
@@ -7,8 +7,8 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#ifndef K3_SEC_PROXY_H
-#define K3_SEC_PROXY_H
+#ifndef SEC_PROXY_H
+#define SEC_PROXY_H
 
 #include <stdint.h>
 
@@ -55,4 +55,4 @@
  */
 int k3_sec_proxy_recv(enum k3_sec_proxy_chan_id id, struct k3_sec_proxy_msg *msg);
 
-#endif /* K3_SEC_PROXY_H */
+#endif /* SEC_PROXY_H */