ARM: at91: remove NEED_MACH_IO_H

The mach/io.h header on at91 is used to support a nonstandard I/O space
window for the cf card driver. This changes the driver to use pci_ioremap_io
in order to have the standard location, and then removes the custom
mach/io.h.

[alexandre.belloni@free-electrons.com: Added PCI dependency]
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>