misc:max8998 Add LDO macros

Add LDO7 and LDO17 macros to max8998_pmic.h necessary to power on the LCD.

Signed-off-by: Piotr Wilczek <p.wilczek@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>