The Integrator has a custom <mach/memory.h> header defining the
BUS_OFFSET for *_to_bus and bus_to_* operations as offset from
0x80000000.

This switches the Integrator over to using the mechanism
introduced for the Keystone to provide the same offset using
the device tree, deletes <mach/memory.h> and augments the
Integrator device tree to provide the bus offset.

Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Jonathan Austin <jonathan.austin@arm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>