glsl: Add nequal() to ir_builder.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>

src/glsl/ir_builder.cpp

@@ -231,6 +231,12 @@ equal(operand a, operand b)
    return expr(ir_binop_equal, a, b);
 }
 
+ir_expression*
+nequal(operand a, operand b)
+{
+   return expr(ir_binop_nequal, a, b);
+}
+
 ir_expression*
 less(operand a, operand b)
 {