qdev: allow multiple qdev_init_gpio_in() calls

qdev: allow multiple qdev_init_gpio_in() calls

Allow multiple qdev_init_gpio_in() calls for the one device. The first call will
define GPIOs 0-N-1, the next GPIOs N- ... . Allows different GPIOs to be handled
with different handlers. Needed when two levels of the QOM class heirachy both
define GPIO functionality, as a single GPIO handler with an index selecter is
not possible.

Signed-off-by: Peter A. G. Crosthwaite <peter.crosthwaite@petalogix.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>