rewrite-expr-grammar.ym: Free up token.

Upsteam-Status: Backport

Reported-by: Xufeng Zhang <xufeng.zhang@windriver.com>
Signed-off-by: Viktor Tusa <tusavik@gmail.com>
---
--- a/lib/rewrite/rewrite-expr-grammar.ym
+++ b/lib/rewrite/rewrite-expr-grammar.ym
@@ -78,6 +78,7 @@
 
 	    $$ = log_template_new(configuration, $1);
 	    CHECK_ERROR(log_template_compile($$, $1, &error), @1, "Error compiling template (%s)", error->message);
+            free($1);
 	  }
 	;