fix opencl INTRATE

No idea why somebody thought pow() would be better than a mere division.
Without this the unittest fails because of a slightly different result.

Change-Id: Ibbde8b872049be310ac98389634aab6eab154ca6
Reviewed-on: https://gerrit.libreoffice.org/64229
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

sc/source/core/opencl/op_financial.cxx

@@ -378,9 +378,8 @@ void OpINTRATE::GenSlidingWindowFunction(std::stringstream& ss,
         }
     }
     ss << "    int nNullDate = GetNullDate();\n";
-    ss << "    tmp = arg3 * pow(arg2,-1) - 1.0;\n";
-    ss << "    tmp = tmp * pow(GetYearDiff_new(nNullDate, (int)arg0,";
-    ss << " (int)arg1,(int)arg4),-1);\n";
+    ss << "    tmp = ((arg3 / arg2) - 1) / GetYearDiff_new(nNullDate, (int)arg0,";
+    ss << "             (int)arg1,(int)arg4);\n";
     ss << "    return tmp;\n";
     ss << "}";
 }