[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/es1968.c b/sound/pci/es1968.c
index 1383798..1bf298d 100644
--- a/sound/pci/es1968.c
+++ b/sound/pci/es1968.c
@@ -2475,7 +2475,8 @@
 static int snd_es1968_free(struct es1968 *chip)
 {
 	if (chip->io_port) {
-		synchronize_irq(chip->irq);
+		if (chip->irq >= 0)
+			synchronize_irq(chip->irq);
 		outw(1, chip->io_port + 0x04); /* clear WP interrupts */
 		outw(0, chip->io_port + ESM_PORT_HOST_IRQ); /* disable IRQ */
 	}