radio-tavarua: Send disable event

Send disable event when FM turn off is completed
so that file descriptor can be released safely

(cherry picked from commit 0fa19849354c41e3ac89ec0b6b3bb411cb69b908)

CRs-Fixed: 339470
Signed-off-by: Ayaz Ahmad <aahmad@codeaurora.org>
(cherry picked from commit d1aead93cddbb53f24f6468185f7c26290b4ffc6)

Change-Id: Ib95580f8cac3cc4c752248932e47c44d82c0e2c5
Signed-off-by: Ramakrishna Prasad N <crpn@codeaurora.org>