radio-iris: Configure repeat count for PS string

- When FM Rx tuned to a station, not receiving complete PS string.
  SOC is not waiting for complete PS string. it is sending PS event
  even if it has part of PS string as well.
- Added support for setting repeat count for PS string
  to get refined PS string from receiver.

CRs-Fixed: 474719
Change-Id: I71c0c1c8af9488573c05d816c37982f9ed935a87
Signed-off-by: Venkateshwarlu Domakonda <Venkateshwarlu@codeaurora.org>