regmap: Updates for v4.6

This has been a very busy release for regmap, not just in cleaning up
the mess we got ourselves into with the endianness handling but also in
other areas too:

 - Fixes for the endianness handling so that we now explicltly default
   to little endian (the code used to do this by accident).  This
   fixes handling of explictly specified endianness on big endian
   systems.
 - Optimisation of the implementation of register striding.
 - A refectoring of the _update_bits() code to reduce duplication.
 - Fixes and enhancements for the interrupt implementation which
   make it easier to use in a wider range of systems.
Merge remote-tracking branch 'regmap/topic/update-bits' into regmap-next