Fix tests; Remove simulation;

- Add -map and -assert options for equiv_opt;
	!!! '-assert' option was commented for the next tests (unproven
$equiv cells was found):
		- dffs;
		- div_mod;
		- latches;
		- mul_pow;
- Add design -load;
- Remove simulations;

tests/ice40/div_mod.v

@@ -0,0 +1,13 @@
+module top
+(
+ input [3:0] x,
+ input [3:0] y,
+
+ output [3:0] A,
+ output [3:0] B
+ );
+
+assign A =  x % y;
+assign B =  x / y;
+
+endmodule