[FM] FM Radio tunes to 100.0 the first time you Stop/Play

Goto All Apps and long-press on FMRadio and slide it to
"App Info" -> Click on "CLEAR DATA" -> Start FM Radio app.
Do not change the station, leave it on whatever the app first
comes up with -> Hit stop button -> Hit Play button, FM radio
tunes to 100.0.

The fix is to update mCurrentStation when FM power up is finished.

Bug 18692583

https://partner-android-review.googlesource.com/#/c/188575/



Change-Id: Ifd9d2e9d6aec61573d001e64d1cf255159ed4970
Signed-off-by: Benson Huang <benson.huang@mediatek.com>