util/nvramtool: Include missing header

The prototype for is_ident() is in this header, so include it.

Change-Id: I45e0d58d1b891b18b3eb7741897ab691188a2bd9
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33947
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

util/nvramtool/accessors/layout-common.c

@@ -26,6 +26,8 @@
 
 #include <ctype.h>
 
+#include "layout-text.h"
+
 static int is_ident_nondigit(int c)
 {
 	int result;