dtc: Remove unused lexer function

dtc does not use the input() function in flex.  Apparently on some gcc
versions the unused function will cause warnings.  Therefore, this
patch removes the function by using the 'noinput' option to flex.

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

dtc-lexer.l

@@ -18,7 +18,7 @@
  *                                                                   USA
  */
 
-%option noyywrap nounput yylineno
+%option noyywrap nounput noinput yylineno
 
 %x INCLUDE
 %x BYTESTRING