ril: Fix unsol response array mapping

 * Instead of messing around with indices, look up
   the requestNumber in the array.
 * This has a cost of O(N) instead of O(1) with the
   previous implementation, but we don't receive unsol
   response codes frequently enough to be worried about
   this.
 * This was needed because a few vendor reponses, aka
   RIL_UNSOL_SNDMGR_WB_AMR_REPORT at index 33 and
   RIL_UNSOL_SNDMGR_CLOCK_CTRL at index 34
   could not be addressed by their array indices anymore
   because we cannot calculate their index by the unsol
   response code we receive from the modem.

Change-Id: I27319e621c777fe19ae8908d7e0c4a46d6dd6d3b