dtc: Use noinput flex option for convert-dtsv0 to remove warning

The convert-dtsv0 lexer doesn't use lex's input() macro/function.
This can result in "defined but not used" warnings.  This patch uses
flex's noinput option to prevent this warning (as we already do for
dtc-lexer.l).

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

convert-dtsv0-lexer.l

@@ -17,7 +17,7 @@
  *                                                                   USA
  */
 
-%option noyywrap nounput
+%option noyywrap nounput noinput
 
 %x INCLUDE
 %x BYTESTRING