mailbox: remove unnecessary platform_set_drvdata()

The driver core clears the driver data to NULL after device_release
or on probe failure. Thus, it is not needed to manually clear the
device driver data to NULL.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
diff --git a/drivers/mailbox/mailbox-omap2.c b/drivers/mailbox/mailbox-omap2.c
index eba380d..42d2b89 100644
--- a/drivers/mailbox/mailbox-omap2.c
+++ b/drivers/mailbox/mailbox-omap2.c
@@ -325,7 +325,6 @@
 	kfree(privblk);
 	kfree(mboxblk);
 	kfree(list);
-	platform_set_drvdata(pdev, NULL);
 
 	return 0;
 }