PocketBeagle2: Switch to gpiod

• So while working on ioctl example. I was looking at the source of both gpio_cdev and gpiod.
• gpio_cdev code quality was not great, and it only used v1 of GPIO ioctl API.
• On the other hand, gpiod source was pretty close to the abstraction I ended up writing. In fact, it was better in some particular cases. So for any serious projects, I think gpiod is a really good option.
• And I can always write wrapper for embedded-hal if needed.
• I still might add ioctl abstraction, but well, yeah, if possible, I think the code quality of this crate is as good as it gets for now.

Signed-off-by: Ayush Singh [email protected]