block: Fix elevator name declaration

The elevator_name field in struct elevator_type is declared as an array
of characters (ELV_NAME_MAX size) but in practice used as a string
pointer with its initialization done statically within each
elevator elevator_type structure declaration.

Change the declaration of elevator_name to the more appropriate
"const char *" type.
Acked-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/elevator.h

@@ -75,7 +75,7 @@ struct elevator_type
 	size_t icq_size;	/* see iocontext.h */
 	size_t icq_align;	/* ditto */
 	struct elv_fs_entry *elevator_attrs;
-	char elevator_name[ELV_NAME_MAX];
+	const char *elevator_name;
 	const char *elevator_alias;
 	struct module *elevator_owner;
 #ifdef CONFIG_BLK_DEBUG_FS