omap: mailbox: trivial cleanups

And fix a few compilation warnings.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Hiroshi DOYU <Hiroshi.DOYU@nokia.com>
diff --git a/arch/arm/mach-omap1/mailbox.c b/arch/arm/mach-omap1/mailbox.c
index 4f5b3da..15bf2a2 100644
--- a/arch/arm/mach-omap1/mailbox.c
+++ b/arch/arm/mach-omap1/mailbox.c
@@ -83,7 +83,7 @@
 	struct omap_mbox1_fifo *fifo =
 		&((struct omap_mbox1_priv *)mbox->priv)->rx_fifo;
 
-	return (mbox_read_reg(fifo->flag));
+	return mbox_read_reg(fifo->flag);
 }
 
 /* irq */