ARM: mach-omap1: Fix omap1510_fpga_init_irq() implicit declarations.

ARM: mach-omap1: Fix omap1510_fpga_init_irq() implicit declarations.

This patch adds a omap1510_fpga_init_irq() inline dummy implementations
in arch/arm/mach-omap1/common.h. Without this patch,build system can
lead to issues. This was discovered during randconfig testing,in which
other than CONFIG_ARCH_OMAP15XX was enabled the leading to the following
error:

CC      arch/arm/mach-omap1/board-innovator.o
arch/arm/mach-omap1/board-innovator.c: In function ‘innovator_init’:
arch/arm/mach-omap1/board-innovator.c:377:3: error: implicit declaration of
function ‘omap1510_fpga_init_irq’ [-Werror=implicit-function-declaration]
cc1: some warnings being treated as errors
make[1]: *** [arch/arm/mach-omap1/board-innovator.o] Error 1
make: *** [arch/arm/mach-omap1] Error 2

Signed-off-by: Manjunath Goudar <csmanjuvijay@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-omap@vger.kernel.org
Signed-off-by: Tony Lindgren <tony@atomide.com>