block: elevator.c: Remove now unused elevator= argument

Since the inclusion of blk-mq, elevator argument was not being
considered anymore, and it's utility died long with the legacy IO path,
now removed too.

Reviewed-by: Hannes Reinecke <[e-mail]>
Reviewed-by: Bob Liu <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Marcos Paulo de Souza <[e-mail]>

Fold with doc removal patch.

Signed-off-by: Jens Axboe <[e-mail]>

Documentation/admin-guide/kernel-parameters.txt

···
 			See comment before function elanfreq_setup() in
 			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 
-	elevator=	[IOSCHED]
-			Format: { "mq-deadline" | "kyber" | "bfq" }
-			See Documentation/block/deadline-iosched.rst,
-			Documentation/block/kyber-iosched.rst and
-			Documentation/block/bfq-iosched.rst for details.
-
 	elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
 			Specifies physical address of start of kernel core
 			image elf header and optionally the size. Generally

block/elevator.c

···
 	return e;
 }
 
-static char chosen_elevator[ELV_NAME_MAX];
-
-static int __init elevator_setup(char *str)
-{
-	/*
-	 * Be backwards-compatible with previous kernels, so users
-	 * won't get the wrong elevator.
-	 */
-	strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
-	return 1;
-}
-
-__setup("elevator=", elevator_setup);
-
 static struct kobj_type elv_ktype;
 
 struct elevator_queue *elevator_alloc(struct request_queue *q,