Make TF UUID RFC 4122 compliant

RFC4122 defines that fields are stored in network order (big endian),
but TF-A stores them in machine order (little endian by default in TF-A).
We cannot change the future UUIDs that are already generated, but we can store
all the bytes using arrays and modify fiptool to generate the UUIDs with
the correct byte order.

Change-Id: I97be2d3168d91f4dee7ccfafc533ea55ff33e46f
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>
diff --git a/drivers/io/io_fip.c b/drivers/io/io_fip.c
index 487f586..1754339 100644
--- a/drivers/io/io_fip.c
+++ b/drivers/io/io_fip.c
@@ -32,7 +32,7 @@
 	fip_toc_entry_t entry;
 } file_state_t;
 
-static const uuid_t uuid_null = {0};
+static const uuid_t uuid_null = { {0} };
 static file_state_t current_file = {0};
 static uintptr_t backend_dev_handle;
 static uintptr_t backend_image_spec;