macintosh/via-pmu: Make some symbols static

The sparse tool complains as follows:

drivers/macintosh/via-pmu.c:183:5: warning:
 symbol 'pmu_cur_battery' was not declared. Should it be static?
drivers/macintosh/via-pmu.c:190:5: warning:
 symbol '__fake_sleep' was not declared. Should it be static?

These symbols are not used outside of via-pmu.c, so this
commit marks them static.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210407125803.4138837-1-yukuai3@huawei.com