doc: Add inclusive language coding guideline

Adds a new inclusive language coding guideline that prohibits
introducing new usage of offensive terms like master/slave and
blacklist/whitelist.

Adds a skeleton table that documents existing usage of offensive terms
and conversion status in affected subsystems. This table is incomplete
and needs to be filled in by subsystem maintainers.

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>