audio: use QTI flac decoder based on flag

 While setting up the component for flac, current design
 is if encoder then don't use QTI flac component otherwise
 use QTI flac component, so if QTI flac is not being used
 then this might be wrong. So enhance the design to use
 QTI flac component only when it is enabled, otherwise use
 default flac component

Change-Id: I57454841611885ae7cdf75896f8297ef8132292e
CRs-Fixed: 916650