mfd: max14577: Add defines for MAX77836 charger

Prepare for adding support for MAX77836 charger to the max14577 charger
driver by adding necessary new defines and prefixes to existing ones.

The MAX77836 uses slightly different values for ChgTyp field of STATUS2
register. On the MAX14577 value of 0x6 is reserved and 0x7 dead battery.
On the MAX77836 the opposite:
 - 0x6 means special charger,
 - 0x7 is reserved.
Regardless of these differences use one common enum
max14577_muic_charger_type.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Andrew Morton <akpm@linux-foundation.org>