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 <[e-mail]>
Acked-by: Suman Anna <[e-mail]>
Signed-off-by: Tony Lindgren <[e-mail]>

drivers/mailbox/mailbox-omap2.c

···
 	kfree(privblk);
 	kfree(mboxblk);
 	kfree(list);
-	platform_set_drvdata(pdev, NULL);
 
 	return 0;
 }