ARM: make mach/io.h include optional

Add a kconfig option NEED_MACH_IO_H to conditionally include mach/io.h.

Basing this on CONFIG_PCI and CONFIG_ISA doesn't quite work. Most ISA
platforms don't need mach/io.h, but ebsa110 does. Most PCI platforms need
mach/io.h for now, but ks8695 doesn't which means i/o accesses are broken.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Nicolas Pitre <nico@linaro.org>