gpio: davinci: Redesign driver to accommodate ngpios in one gpio chip

The Davinci GPIO driver is implemented to work with one monolithic
Davinci GPIO platform device which may have up to Y(144) gpios.
The Davinci GPIO driver instantiates number of GPIO chips with
max 32 gpio pins per each during initialization and one IRQ domain.
So, the current GPIO's  opjects structure is:

<platform device> Davinci GPIO controller
 |- <gpio0_chip0> ------|
 ...                    |--- irq_domain (hwirq [0..143])
 |- <gpio0_chipN> ------|

Current driver creates one chip for every 32 GPIOs in a controller.
This was a limitation earlier now there is no need for that. Hence
redesigning the driver to create one gpio chip for all the ngpio
in the controller.

|- <gpio0_chip0> ------|--- irq_domain (hwirq [0..143]).

The previous discussion on this can be found here:
https://www.spinics.net/lists/linux-omap/msg132869.html

Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>