ARM: OMAP: Fix devexit for dma when CONFIG_HOTPLUG is not set

Otherwise we get:

`omap_system_dma_remove' referenced in section `.data' of arch/arm/plat-omap/built-in.o:
defined in discarded section `.devexit.text' of arch/arm/plat-omap/built-in.o

Signed-off-by: Tony Lindgren <tony@atomide.com>
diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c
index 002fb4d..cb856fe 100644
--- a/arch/arm/plat-omap/dma.c
+++ b/arch/arm/plat-omap/dma.c
@@ -2125,7 +2125,7 @@
 
 static struct platform_driver omap_system_dma_driver = {
 	.probe		= omap_system_dma_probe,
-	.remove		= omap_system_dma_remove,
+	.remove		= __devexit_p(omap_system_dma_remove),
 	.driver		= {
 		.name	= "omap_dma_system"
 	},