[U-Boot] [PATCH v4 4/7] env: add check/apply logic to himport_r()

Change hashtable so that a callback function will decide whether a variable can be overwritten, and possibly apply the changes. So add a new field to struct hsearch_data: o apply callback function to check whether a variable can be overwritten, and possibly immediately apply the changes;

Re: [U-Boot] [PATCH v4 4/7] env: add check/apply logic to himport_r()

Dear Gerlando Falauto, Change hashtable so that a callback function will decide whether a variable can be overwritten, and possibly apply the changes. So add a new field to struct hsearch_data: o apply callback function to check whether a variable can be overwritten, and possibly