ubd: remove dead code in ubd_setup_common

Remove some leftovers of the fake major number parsing that cause
complains from some compilers.

Fixes: 2933a1b2c6f3 ("ubd: remove the code to register as the legacy IDE driver")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210628093937.1325608-1-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

arch/um/drivers/ubd_kern.c

@@ -243,22 +243,12 @@ static int ubd_setup_common(char *str, int *index_out, char **error_out)
 	if(index_out) *index_out = -1;
 	n = *str;
 	if(n == '='){
-		char *end;
-		int major;
-
 		str++;
 		if(!strcmp(str, "sync")){
 			global_openflags = of_sync(global_openflags);
 			return err;
 		}
 
-		err = -EINVAL;
-		major = simple_strtoul(str, &end, 0);
-		if((*end != '\0') || (end == str)){
-			*error_out = "Didn't parse major number";
-			return err;
-		}
-
 		pr_warn("fake major not supported any more\n");
 		return 0;
 	}