FROMGIT: power: supply: Allow charger manager can be built as a module

Allow charger manager can be built as a module like other charger
drivers.

Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/lkml/5e098be25c70e07c37e743f84a901f6f756090e0
.1583461755.git.baolin.wang7@gmail.com/
(cherry picked from commit 241eaabc3c315cdfea505725a43de848f498527f
https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next

)
Bug: 148055746
Signed-off-by: Orson Zhai <orson.zhai@unisoc.com>
Change-Id: I2dbe3d09a4779c64ca2508417e819428638a3629