ARM: Kconfig: set default gpio number for rockchip SoCs

The new rk3288 needs a bigger gpio space, as it has 9 gpio banks.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Tested-by: Doug Anderson <dianders@chromium.org>
Tested-by: Will Deacon <will.deacon@arm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>