regmap: Supply ranges to the sync operations

In order to allow us to support partial sync operations add minimum and
maximum register arguments to the sync operation and update the rbtree
and lzo caches to use this new information. The LZO implementation is
obviously not good, we could exit the iteration earlier, but there may
be room for more wide reaching optimisation there.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>