ARM: dts: add ngpios for vf610 compatible gpio controllers

After commit da5dd31e ("gpio: vf610: Switch to gpio-mmio"),
the vf610 GPIO driver no longer uses the static number 32 for
gc->ngpio. This allows users to configure the number of GPIOs
per port.

And some gpio controllers did have less pads. So add 'ngpios' here,
this can save some memory when request bitmap, and also show user
more accurate information when use gpio tools.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>