Don't fail AAC decoding if DRC parameter isn't available

The DRC parameter has been introduced by
I50fcc5ef35cb7e96592c2267652228b5fa074ba9, and is parsed by vendor.
Vendors prior to this commit are supposed to fail this request.

Anyway, assume this isn't an error, and simply ignore DRC parameters if
vendor doesn't support this.

Change-Id: I117411ad7063e24a7d01de90774d5ca1f5dc4bea