cppcheck: fix duplicate if/else

I don't know if it's possible to parse EBCDIC knowing that there are several implementations
So I commented the block and added a TODO.
=> no time wasted for this block (ok "micro waste")+ 1 less cppcheck report

Change-Id: I72b72b68295eab7be5332166b955adaddf6ee5c3

sax/source/expatwrap/xml2utf.cxx

@@ -314,12 +314,14 @@ sal_Bool XMLFile2UTFConverter::scanForEncoding( Sequence< sal_Int8 > &seq )
         // UCS-4 little endian
         m_sEncoding = "ucs-4";
     }
+/* TODO: no need to test for the moment since we return sal_False like default case anyway
     else if( 0x4c == pSource[0] && 0x6f == pSource[1]  &&
              0xa7 == static_cast<unsigned char> (pSource[2]) &&
              0x94 == static_cast<unsigned char> (pSource[3]) ) {
         // EBCDIC
         bReturn = sal_False;   // must be extended
     }
+*/
     else {
         // other
         // UTF8 is directly recognized by the parser.