nvme: fixup scan failure for non-ANA multipath controllers

Commit 62baf70 caused the ANA log page to be re-read, even on
controllers that do not support ANA.  While this should generally
harmless, some controllers hang on the unsupported log page and
never finish probing.

Fixes: 62baf70 ("nvme: re-read ANA log page after ns scan completes")
Signed-off-by: Hannes Reinecke <hare@kernel.org>
Tested-by: Srikanth Aithal <sraithal@amd.com>
[hch: more detailed commit message]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/host/core.c

@@ -4300,7 +4300,7 @@ static void nvme_scan_work(struct work_struct *work)
 	if (test_bit(NVME_AER_NOTICE_NS_CHANGED, &ctrl->events))
 		nvme_queue_scan(ctrl);
 #ifdef CONFIG_NVME_MULTIPATH
-	else
+	else if (ctrl->ana_log_buf)
 		/* Re-read the ANA log page to not miss updates */
 		queue_work(nvme_wq, &ctrl->ana_work);
 #endif