[sw] Format include guards in the SW tree

Signed-off-by: Miguel Young de la Sota <mcyoung@google.com>
diff --git a/sw/device/lib/hw_sha256.h b/sw/device/lib/hw_sha256.h
index aa066e2..e28f2d5 100644
--- a/sw/device/lib/hw_sha256.h
+++ b/sw/device/lib/hw_sha256.h
@@ -2,8 +2,8 @@
 // Licensed under the Apache License, Version 2.0, see LICENSE for details.
 // SPDX-License-Identifier: Apache-2.0
 
-#ifndef _F_LIB_SHA256_H__
-#define _F_LIB_SHA256_H__
+#ifndef OPENTITAN_SW_DEVICE_LIB_HW_SHA256_H_
+#define OPENTITAN_SW_DEVICE_LIB_HW_SHA256_H_
 
 #include <stddef.h>
 
@@ -47,4 +47,4 @@
  */
 const uint8_t *hw_SHA256_hash(const void *data, size_t len, uint8_t *digest);
 
-#endif  // _F_LIB_SHA256_H__
+#endif  // OPENTITAN_SW_DEVICE_LIB_HW_SHA256_H_