Format UUID strings correctly

Prior to this patch although GlobalPlatform specifies that TAs and such
are identified with UUIDs, we don't format them quite right when turning
them into strings. Per https://www.ietf.org/rfc/rfc4122.txt, there
should be another hyphen after the first two bytes of clockSeqAndNode.

Unfortunately, fixing this breaks compatibility between how TAs are
built, and when the OS loads them.

With this patch UUID string are formated with the additional hyphen as
for instance: f81d4fae-7dec-11d0-a765-00a0c91e6bf6

Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Fixes: OP-TEE/optee_os#857
Tested-by: Jens Wiklander <jens.wiklander@linaro.org> (QEMU)
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

lib/libutils/ext/snprintk.c

@@ -80,7 +80,7 @@
 #define NOLOCK        0x1000	/* don't acquire a tty lock */
 
 /* max size buffer kprintf needs to print a UUID */
-#define KPRINTF_BUFSIZE        36
+#define KPRINTF_BUFSIZE        37
 
 /*
  * The following macro is used to remove const cast-away warnings
@@ -220,7 +220,7 @@ static int uuid2str(char *dst, size_t size, void *ptr)
 	} *uuid = ptr;
 
 	return snprintk(dst, size,
-			"%08x-%04x-%04x-%02x%02x%02x%02x%02x%02x%02x%02x",
+			"%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
 			uuid->lo, uuid->mid, uuid->hi_ver,
 			uuid->seq_n[0], uuid->seq_n[1],
 			uuid->seq_n[2],	uuid->seq_n[3],