gpio: document polarity flag best practices
gpio: document polarity flag best practices

Document what we (Laurent and I, following a mailing list dicussion)
believe are best practices for the polarity flag in a GPIO specifier.

While touching the doc, I made a few minor editing changes to other
areas.

Suggested-by: Laurent Pinchart <3ded2f39a78f0d7044839546f95841842b4d7c96@ideasonboard.com>
Signed-off-by: Stephen Warren <5ef2a23ba3aff51d1cfc8c113c1ec34b608b3b13@nvidia.com>
Acked-by: Laurent Pinchart <3ded2f39a78f0d7044839546f95841842b4d7c96@ideasonboard.com>
Signed-off-by: Linus Walleij <9cd9d802d23c0ed5e224beabf4ae4a5c478746ef@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs