gpio updates for v5.7 part 4
- improve comments in the uapi header
- fix documentation issues
- add a warning to gpio-pl061 when the IRQ line is not configured
- allow building gpio-mxc and gpio-mxs with COMPILE_TEST enabled
- don't print an error message when an optional IRQ is missing in gpio-mvebu
- fix a potential segfault in gpio-hammer
- fix a couple typos and coding style issues in gpio tools
- provide a new flag in gpio-mmio and use it in mt7621 to fix an issue with
the controller ignoring value setting when a GPIO is in input mode
- slightly refactor gpio_name_to_desc()