UPSTREAM: i2c: document generic DT bindings for timing parameters

UPSTREAM: i2c: document generic DT bindings for timing parameters

Also, sort the properties alphabetically and make indentation
consistent. Wording largely taken from i2c-rk3x.txt, thanks guys!

Only "i2c-scl-internal-delay-ns" is new, the rest is used by two drivers
already and was documented in their driver binding documentation.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
(cherry picked from commit 99b809d7bdd17de7a68f1625a8973052c8311657)

Change-Id: I7f60b372e5ec2425ef6976306a7e26a1437f0384