Revert "scsi: storvsc: Validate length of incoming packet in storvsc_on_channel_callback()"

This reverts commit 3b8c72d0.

Dexuan reported a regression where StorVSC fails to probe a device (and
where, consequently, the VM may fail to boot).  The root-cause analysis led
to a long-standing race condition that is exposed by the validation /commit
in question.  Let's put the new validation aside until a proper solution
for that race condition is in place.

Link: https://lore.kernel.org/r/20201211131404.21359-1-parri.andrea@gmail.com
Fixes: 3b8c72d0 ("scsi: storvsc: Validate length of incoming packet in storvsc_on_channel_callback()")
Cc: Dexuan Cui <decui@microsoft.com>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/storvsc_drv.c

@@ -1246,11 +1246,6 @@ static void storvsc_on_channel_callback(void *context)
 		request = (struct storvsc_cmd_request *)
 			((unsigned long)desc->trans_id);
 
-		if (hv_pkt_datalen(desc) < sizeof(struct vstor_packet) - vmscsi_size_delta) {
-			dev_err(&device->device, "Invalid packet len\n");
-			continue;
-		}
-
 		if (request == &stor_device->init_request ||
 		    request == &stor_device->reset_request) {
 			memcpy(&request->vstor_packet, packet,