scsi: scsi_dh_alua: Fix memleak for 'qdata' in alua_activate()

If alua_rtpg_queue() failed from alua_activate(), then 'qdata' is not
freed, which will cause following memleak:

unreferenced object 0xffff88810b2c6980 (size 32):
comm "kworker/u16:2", pid 635322, jiffies 4355801099 (age 1216426.076s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
40 39 24 c1 ff ff ff ff 00 f8 ea 0a 81 88 ff ff @9$.............
backtrace:
[<0000000098f3a26d>] alua_activate+0xb0/0x320
[<000000003b529641>] scsi_dh_activate+0xb2/0x140
[<000000007b296db3>] activate_path_work+0xc6/0xe0 [dm_multipath]
[<000000007adc9ace>] process_one_work+0x3c5/0x730
[<00000000c457a985>] worker_thread+0x93/0x650
[<00000000cb80e628>] kthread+0x1ba/0x210
[<00000000a1e61077>] ret_from_fork+0x22/0x30

Fix the problem by freeing 'qdata' in error path.

Fixes: 625fe857e4fa ("scsi: scsi_dh_alua: Check scsi_device_get() return value")
Signed-off-by: Yu Kuai <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Benjamin Block <[e-mail]>
Reviewed-by: Bart Van Assche <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/device_handler/scsi_dh_alua.c

···
 	rcu_read_unlock();
 	mutex_unlock(&h->init_mutex);
 
-	if (alua_rtpg_queue(pg, sdev, qdata, true))
+	if (alua_rtpg_queue(pg, sdev, qdata, true)) {
 		fn = NULL;
-	else
+	} else {
+		kfree(qdata);
 		err = SCSI_DH_DEV_OFFLINED;
+	}
 	kref_put(&pg->kref, release_port_group);
 out:
 	if (fn)