libzfs_pool: Remove unused check for ENOTBLK

Commit 379ca9c removed the check on aux devices to be block devices also
changing zfs_ioctl(hdl, ZFS_IOC_VDEV_ADD, ...) and
zfs_ioctl(hdl, ZFS_IOC_POOL_CREATE, ...) to never set ENOTBLK. This
change removes the dangling check for ENOTBLK that will never trigger.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reported-by: Richard Elling <Richard.Elling@RichardElling.com>
Signed-off-by: Alex John <alex@stty.io>
Closes #10173

lib/libzfs/libzfs_pool.c

@@ -1351,11 +1351,6 @@ zpool_create(libzfs_handle_t *hdl, const char *pool, nvlist_t *nvroot,
 			    "one or more devices is out of space"));
 			return (zfs_error(hdl, EZFS_BADDEV, msg));
 
-		case ENOTBLK:
-			zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
-			    "cache device must be a disk or disk slice"));
-			return (zfs_error(hdl, EZFS_BADDEV, msg));
-
 		default:
 			return (zpool_standard_error(hdl, errno, msg));
 		}
@@ -1543,12 +1538,6 @@ zpool_add(zpool_handle_t *zhp, nvlist_t *nvroot)
 			(void) zfs_error(hdl, EZFS_BADVERSION, msg);
 			break;
 
-		case ENOTBLK:
-			zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
-			    "cache device must be a disk or disk slice"));
-			(void) zfs_error(hdl, EZFS_BADDEV, msg);
-			break;
-
 		default:
 			(void) zpool_standard_error(hdl, errno, msg);
 		}