ARM: ixp4xx: include irqs.h where needed

Multiple ixp4xx specific files require macros from irqs.h that
were moved out from mach/irqs.h, e.g.:

arch/arm/mach-ixp4xx/vulcan-pci.c:41:19: error: this function declaration is not a prototype [-Werror,-Wstrict-prototypes]
arch/arm/mach-ixp4xx/vulcan-pci.c:49:10: error: implicit declaration of function 'IXP4XX_GPIO_IRQ' [-Werror,-Wimplicit-function-declaration]
                return IXP4XX_GPIO_IRQ(INTA);

Include this header in all files that failed to build because of
that.

Fixes: dc8ef8cd

 ("ARM: ixp4xx: Convert to SPARSE_IRQ")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Olof Johansson <olof@lixom.net>