gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL
Add support for requesting lines using the GPIO_V2_GET_LINE_IOCTL, and returning their current values using GPIO_V2_LINE_GET_VALUES_IOCTL. The struct linereq implementation is based on the v1 struct linehandle implementation. Signed-off-by: Kent Gibson <warthog618@gmail.com> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>