power: max17050: check version of custom parameters

To update custom parameters without fuel gauge's
POR(Power on reset), define and store the version
of custom parameters to the unused register, 0x20
register. MAXIM confirmed the 0x20 register can be
used for this purpose. By checking this version,
driver can detect the change of the parameters and
update them without POR.

For use of userspace, add sysfs entries which pass the
status of init done and power on reset.

Change-Id: I0ee008d75f722d44449c85fe1a18b550ceed7126
Signed-off-by: choongryeol.lee <choongryeol.lee@lge.com>