power: supply: cw2015: Make some symbols static

Fix the following warning:

drivers/power/supply/cw2015_battery.c:96:5: warning:
'cw_update_profile' was not declared. Should it be static?
drivers/power/supply/cw2015_battery.c:712:1: warning:
'cw_bat_pm_ops' was not declared. Should it be static?

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: ChenTao <chentao107@huawei.com>
Acked-by: Tobias Schramm <t.schramm@manjaro.org>
Tested-by: Tobias Schramm <t.schramm@manjaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>