Remove redundant YYLOC global declaration

Same as the upstream fix for building dtc with gcc 10.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>

scripts/dtc/dtc-lexer.l

@@ -38,7 +38,6 @@ LINECOMMENT	"//".*\n
 #include "srcpos.h"
 #include "dtc-parser.tab.h"
 
-YYLTYPE yylloc;
 extern bool treesource_error;
 
 /* CAUTION: this will stop working if we ever use yyless() or yyunput() */