[FM] Radio text is not updated in notification bar

Launch FM and play a station with program service(PS) and
radio text(RT) -> Use siliab tool to rename the PS and RT
as null string -> Press home button and pull down notification
bar -> Check the FM information in notification bar, radio
text is not updated in notification bar.

The fix is to let radio text been updated in notifcation bar
when radio text is changed.

https://partner-android-review.git.corp.google.com/#/c/188806/



Bug 18762405

Change-Id: I77f4ec5cd9459fabfec63f7e236a7bc96cd79f13
Signed-off-by: Benson Huang <benson.huang@mediatek.com>