audioflinger: Use offloaded effects in case of PCM offload

These lines are not available in AOSP, so when d5ee6cee
("DO NOT MERGE - improve audio effect framwework thread safety") was
applied, they were left behind and currently don't make any difference.

Change-Id: I73c3eaa2f3a67fe8cbbb9b59473c85c838ecbf77