ALSA: powermac: Remove redundant platform_set_drvdata()

Commit 0998d06310 (device-core: Ensure drvdata = NULL when no
driver is bound) removes the need to set driver data field to
NULL.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/ppc/powermac.c b/sound/ppc/powermac.c
index 09fc848..8abb521 100644
--- a/sound/ppc/powermac.c
+++ b/sound/ppc/powermac.c
@@ -139,7 +139,6 @@
 static int snd_pmac_remove(struct platform_device *devptr)
 {
 	snd_card_free(platform_get_drvdata(devptr));
-	platform_set_drvdata(devptr, NULL);
 	return 0;
 }