[FM] FM default name of recording file is not correct

    Launch FM, play a channel without a name or PS info ->
    Select "Start Recording" in options menu -> Tap "STOP
    RECORDINGS" and check the default name, It is
    "FM__MMddyyyy_hhmmss".

    The fix is to change recordingName according to different
    condition.

    Bug 18780825

    Review: https://partner-android-review.git.corp.google.com/#/c/189540



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

Change-Id: I75a3565f689f552e4965ede900f07f68749ed736