FM: Convert notifications to use NotificationChannel

Usecase:
Turn on FM or scan for channels

Expected Behaviour:
Notification popup for FM should be displayed on Notification UI

Observed Behaviour:
Notification popup for FM is not displayed on Notifcation UI &
(developer warning)Toast message is shown on FM radio screen
while showing notification

Root cause:
In Android O, notifications are hidden by default.
This must be changed to use notification channels so that the
priority of the notifications can be updated.

Fix:
Add notification channel before building notification from FM.

CRs-fixed: 2063780
Change-Id: I13cd782ac0bdd4ec8bc2097f7f874a1ae1fb246b
1 file changed