hal: Fix 44.1Khz playback when native support is not enabled

-Currently, backend sampling rate is incorrectly set to 44.1Khz - for
 24b/44.1Khz clips - when native support is not available. SLIM_0_RX
 doesn't support native playback. By setting the backend to 48Khz,
 audio playback works as expected.
-Initialize and update return value before returning

Change-Id: I35f05e78b02159ff046da6c0d70dcd53f6464c8e
CRs-Fixed: 963693