Changes name of iv_check to iv_len_validity

Commit changes name of check_iv to
iv_len_validity as this seems to better describe
its functionality.

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/tests/suites/test_suite_cipher.function b/tests/suites/test_suite_cipher.function
index 615658e..2f352c1 100644
--- a/tests/suites/test_suite_cipher.function
+++ b/tests/suites/test_suite_cipher.function
@@ -1148,7 +1148,7 @@
 /* END_CASE */
 
 /* BEGIN_CASE */
-void check_iv( int cipher_id, char * cipher_string,
+void iv_len_validity( int cipher_id, char * cipher_string,
                int iv_len_val, int ret )
 {
     size_t iv_len = iv_len_val;