regmap: Updates for v4.11

For v4.11 activity on the regmap API has literally doubled, there are
two patches this release:

  - Fixes from Charles Keepax to make the kerneldoc generate correctly.
  - A cleanup from Geliang Tang using rb_entry() rather than open coding
    it with container_of().
Merge remote-tracking branches 'regmap/topic/doc' and 'regmap/topic/rbtree' into regmap-next