USHRT_MAX -> SAL_MAX_UINT16

nArgCount apparently must fit into sal_uInt16 for the cast further down when
assigning it to sal_uInt16 ScFuncDesc::nArgCount

Change-Id: Ie82f864d519589553505015dc577b1e3372293b2
Reviewed-on: https://gerrit.libreoffice.org/48836Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

sc/source/core/tool/addincol.cxx

@@ -1224,7 +1224,7 @@ bool ScUnoAddInCollection::FillFunctionDescFromData( const ScUnoAddInFuncData& r
     bool bIncomplete = !rFuncData.GetFunction().is();       //TODO: extra flag?
 
     long nArgCount = rFuncData.GetArgumentCount();
-    if ( nArgCount > USHRT_MAX )
+    if ( nArgCount > SAL_MAX_UINT16 )
         return false;
 
     if ( bIncomplete )