ARM: dts: keystone-k2g: Add gpio nodes

66AK2G has 2 instances of gpio. The first one has all the 144 GPIOs
functional. 9 banks with 16 gpios making a total of 144. The second
instance has only the GPIO0:GPIO67 functional and rest are marked
reserved.

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