gpiolib: check the 'ngpios' property in core gpiolib code

[ Upstream commit 9dbd1ab2 ]

Several drivers read the 'ngpios' device property on their own, but
since it's defined as a standard GPIO property in the device tree bindings
anyway, it's a good candidate for generalization. If the driver didn't
set its gc->ngpio, try to read the 'ngpios' property from the GPIO
device's firmware node before bailing out.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Stable-dep-of: ec851b23 ("gpiolib: fix memory leak in gpiochip_setup_dev()")
Signed-off-by: Sasha Levin <sashal@kernel.org>