Correct styling of Mbed TLS in documentation

Several bits of documentation were incorrectly styling Mbed TLS
as MbedTLS.

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/tests/src/external_timing/timing_alt.h b/tests/src/external_timing/timing_alt.h
index 82e8c8b..d71ceb9 100644
--- a/tests/src/external_timing/timing_alt.h
+++ b/tests/src/external_timing/timing_alt.h
@@ -1,5 +1,5 @@
 /*
- * Copy of the internal MbedTLS timing implementation, to be used in tests.
+ * Copy of the internal Mbed TLS timing implementation, to be used in tests.
  */
 /*
  *  Copyright The Mbed TLS Contributors