regmap: Introduce regmap_get_max_register

This patch introduces regmap_get_max_register() function which would be
used by the infrastructures like nvmem framework built on top of
regmap.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --cc drivers/base/regmap/regmap.c
Simple merge

diff --cc include/linux/regmap.h
Simple merge