Test drivers: rename import call source to driver location

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/tests/include/test/drivers/key_management.h b/tests/include/test/drivers/key_management.h
index 38298ae..c8dfbb3 100644
--- a/tests/include/test/drivers/key_management.h
+++ b/tests/include/test/drivers/key_management.h
@@ -42,8 +42,8 @@
     /* Count the amount of times one of the key management driver functions
      * is called. */
     unsigned long hits;
-    /* Record the source of the function call. */
-    psa_key_location_t source;
+    /* Location of the last key management driver called to import a key. */
+    psa_key_location_t location;
 } mbedtls_test_driver_key_management_hooks_t;
 
 /* The location is initialized to the invalid value 0x800000. Invalid in the