OMAP: mach-omap2: Fix miscellaneous sparse warnings

This patch fixes miscellaneous sparse warnings in mach-omap2.

arch/arm/mach-omap2/board-am3517evm.c:141:17: warning: Initializer entry defined twice
arch/arm/mach-omap2/board-am3517evm.c:142:18:   also defined here

arch/arm/mach-omap2/irq.c:50:35: warning: Using plain integer as NULL pointer

Signed-off-by: Manjunath Kondaiah G <manjugk@ti.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>