cam/scsi: Add sysctl flag CTLFLAG_TUN to loader tunable

The sysctl variable 'kern.cam.scsi_delay' is actually a loader tunable.
Add sysctl flag CTLFLAG_TUN to it so that `sysctl -T` will report it
correctly.

No functional change intended.

Reviewed by:	kib, imp (for #cam)
Approved by:	re (gjb)
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D42113

(cherry picked from commit e2ad7ce37b)
(cherry picked from commit 4bf3810546)

sys/cam/scsi/scsi_all.c

@@ -9406,7 +9406,8 @@ sysctl_scsi_delay(SYSCTL_HANDLER_ARGS)
 	return (set_scsi_delay(delay));
 }
 SYSCTL_PROC(_kern_cam, OID_AUTO, scsi_delay,
-    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0, sysctl_scsi_delay, "I",
+    CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE,
+    0, 0, sysctl_scsi_delay, "I",
     "Delay to allow devices to settle after a SCSI bus reset (ms)");
 
 static int