[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/ens1370.c b/sound/pci/ens1370.c
index 52fae4a..fbf1124 100644
--- a/sound/pci/ens1370.c
+++ b/sound/pci/ens1370.c
@@ -1910,7 +1910,8 @@
 	outl(0, ES_REG(ensoniq, CONTROL));	/* switch everything off */
 	outl(0, ES_REG(ensoniq, SERIAL));	/* clear serial interface */
 #endif
-	synchronize_irq(ensoniq->irq);
+	if (ensoniq->irq >= 0)
+		synchronize_irq(ensoniq->irq);
 	pci_set_power_state(ensoniq->pci, 3);
       __hw_end:
 #ifdef CHIP1370