smb347-charger: Rename few functions to match better what they are doing

The naming used in the driver for some functions is not very clear what
the functions are really doing. To make this a bit easier to understand
we rename few functions which were badly named.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>