Remove unused init(Phone) and some cleanup in SubscriptionController

Remove init(Phone) in SubscriptionController. This CL includes small
cleanup as follows.
 - Fix SubscriptionController description.
 - Fix some style issue.
 - Remove slog() and used logd() instead.

Test: Build

Change-Id: I5c6d4f967918d570087f94b0ae32bec5dfcd7c4b
Signed-off-by: Taesu Lee <taesu82.lee@samsung.com>