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/include/drivers/marvell/thermal.h b/include/drivers/marvell/thermal.h
index 191f97b..48376a7 100644
--- a/include/drivers/marvell/thermal.h
+++ b/include/drivers/marvell/thermal.h
@@ -7,8 +7,8 @@
 
 /* Driver for thermal unit located in Marvell ARMADA 8K and compatible SoCs */
 
-#ifndef _THERMAL_H
-#define _THERMAL_H
+#ifndef THERMAL_H
+#define THERMAL_H
 
 struct tsen_config {
 	/* thermal temperature parameters */
@@ -28,4 +28,4 @@
 int marvell_thermal_read(struct tsen_config *tsen_cfg, int *temp);
 struct tsen_config *marvell_thermal_config_get(void);
 
-#endif /* _THERMAL_H */
+#endif /* THERMAL_H */