Rework notification LED a bit.

* Clean up code, improve logic.

PS6: According to android writing style update string for "OK"
     https://developer.android.com/design/style/writing.html
PS7: Whitespaces.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>
Change-Id: I5408d895b52255a8352ebe8ea1a79be92af9c1a1