mfd: max77693: Set proper maximum register for MUIC regmap

The MUIC block in max77693 has different I2C address than PMIC. The
driver allocated two regmaps: for PMIC and MUIC. However it used the
same regmap_config (with max_register field) for both regmaps. Actual
maximum address of register for MUIC is different than for PMIC.

Define another regmap_config for MUIC with proper max_register value.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>