ath10k: ath10k_pci_init_irq(): workaround for checkpatch fallthrough warning

Latest checkpatch complains about use of fall-through comment. But as this is a
switch statement just reword the comment to workaround the problem.
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1603802288-21158-2-git-send-email-kvalo@codeaurora.org

drivers/net/wireless/ath/ath10k/pci.c

@@ -3236,7 +3236,7 @@ static int ath10k_pci_init_irq(struct ath10k *ar)
 		if (ret == 0)
 			return 0;
 
-		/* fall-through */
+		/* MHI failed, try legacy irq next */
 	}
 
 	/* Try legacy irq