Add single-bit difference tests

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/suites/test_suite_constant_time.data b/tests/suites/test_suite_constant_time.data
index 1b0b964..785bdec 100644
--- a/tests/suites/test_suite_constant_time.data
+++ b/tests/suites/test_suite_constant_time.data
@@ -91,6 +91,9 @@
 mbedtls_ct_memcmp len 17 offset 3
 mbedtls_ct_memcmp:-1:17:3
 
+mbedtls_ct_memcmp_single_bit_diff
+mbedtls_ct_memcmp_single_bit_diff:
+
 mbedtls_ct_memcpy_if len 1 offset 0
 mbedtls_ct_memcpy_if:1:1:0