efi/esrt: remove esre_attribute::store()

esre_attribute::store() is not needed since commit af97a77 (efi:
Move some sysfs files to be read-only by root). Drop it.

Found by https://github.com/jirislaby/clang-struct.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-efi@vger.kernel.org
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/esrt.c

@@ -75,8 +75,6 @@ static LIST_HEAD(entry_list);
 struct esre_attribute {
 	struct attribute attr;
 	ssize_t (*show)(struct esre_entry *entry, char *buf);
-	ssize_t (*store)(struct esre_entry *entry,
-			 const char *buf, size_t count);
 };
 
 static struct esre_entry *to_entry(struct kobject *kobj)