Matmul unroll 2 should change loop bound into 16 since it unrolled

[joyliu37]

clockwork/example_progs/matmul.cpp

Lines 57 to 58 in 5c41205

	auto mul_s1_r_x_rxo = mul_s1_y->add_loop("mul_s1_r_x_rxo", 0, 32);
	auto mul_s1_x_xo = mul_s1_r_x_rxo->add_loop("mul_s1_x_xo", 0, 32);