radio: tavarua: Handle search list event properly

- Not sending the search list event to the userspace when the SOC
  returns 0 channels.
- State machine will be in search state even though the SOC
  return search list event.
- Queue the search list event to the userspace even when the SOC
  returns 0 channels.

Change-Id: Ie69d05341c67d99434cf5ed7badd7242706441bb
CRs-Fixed: 472785
Signed-off-by: Venkateshwarlu Domakonda <Venkateshwarlu@codeaurora.org>