Move constant_flow.h into the main library

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/suites/test_suite_bignum_mod.function b/tests/suites/test_suite_bignum_mod.function
index 4edc0b9..f166079 100644
--- a/tests/suites/test_suite_bignum_mod.function
+++ b/tests/suites/test_suite_bignum_mod.function
@@ -4,7 +4,7 @@
 #include "bignum_mod.h"
 #include "bignum_mod_raw.h"
 #include "constant_time_internal.h"
-#include "test/constant_flow.h"
+#include "constant_flow.h"
 
 #define TEST_COMPARE_MPI_RESIDUES(a, b) \
     ASSERT_COMPARE((a).p, (a).limbs * sizeof(mbedtls_mpi_uint), \