ARM/gpio: ep93xx: build standalone

As a preparation for multiplatform support, this ensures
that the ep93xx gpio driver can be built without any of
the platform specific header files. We pass the IRQ numbers
as a resource now, and use the virtual mmio base from the
already existing resource, rather than relying on the
hardwired virtual address from the header file.

Some numbers are now hardcoded that came from macros
in the past, but for all I can tell, the driver already
relied on the specific values.

Cc: arm@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>