Convert shark to use the fixed i/o mapping and remove io.h.

This shrinks the mapping from 256MB to 1MB, but nothing is using that much
space AFAICT.
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Cc: Russell King <linux@arm.linux.org.uk>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>