Replace references to Mbed Crypto with Mbed TLS through-out documentation and comments.

Signed-off-by: Fredrik Hesse <fredrik@hesse.se>
diff --git a/tests/src/psa_exercise_key.c b/tests/src/psa_exercise_key.c
index 0843e24..6b73486 100644
--- a/tests/src/psa_exercise_key.c
+++ b/tests/src/psa_exercise_key.c
@@ -72,7 +72,7 @@
     psa_key_slot_number_t slot_number = 0xec94d4a5058a1a21;
     psa_status_t status = psa_get_key_slot_number(&attributes, &slot_number);
     if (lifetime_is_dynamic_secure_element(lifetime)) {
-        /* Mbed Crypto currently always exposes the slot number to
+        /* Mbed TLS currently always exposes the slot number to
          * applications. This is not mandated by the PSA specification
          * and may change in future versions. */
         TEST_EQUAL(status, 0);