[ALSA] Fix synchronize_irq() bugs, redundancies

free_irq() calls synchronize_irq() for you, so there is no need for
drivers to manually do the same thing (again).  Thus, calls where
sync-irq immediately precedes free-irq can be simplified.

However, during this audit several bugs were noticed, where free-irq is
preceded by a "irq >= 0" check... but the sync-irq call is not covered
by the same check.

So, where sync-irq could not be eliminated completely, the missing check
was added.

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/ali5451/ali5451.c b/sound/pci/ali5451/ali5451.c
index fc04d3d..1a0fd65 100644
--- a/sound/pci/ali5451/ali5451.c
+++ b/sound/pci/ali5451/ali5451.c
@@ -2047,10 +2047,8 @@
 {
 	if (codec->hw_initialized)
 		snd_ali_disable_address_interrupt(codec);
-	if (codec->irq >= 0) {
-		synchronize_irq(codec->irq);
+	if (codec->irq >= 0)
 		free_irq(codec->irq, codec);
-	}
 	if (codec->port)
 		pci_release_regions(codec->pci);
 	pci_disable_device(codec->pci);