usb: gadget: pxa25x_udc cleanup

This removes the dependency on the mach/hardware.h header file
from the pxa25x_udc driver after the register definitions were
already unified in the previous patch.

Following the model of pxa27x_udc (and basically all other drivers
in the kernel), we define the register numbers as offsets from
the register base address and use accessor functions to read/write
them.

For the moment, this still leaves the direct pointer dereference
in place, instead of using readl/writel, so this patch should
not be changing the behavior of the driver, other than using
ioremap() on the platform resource to replace the hardcoded
virtual address pointers.

Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Felipe Balbi <balbi@kernel.org>