relax effects library path in audio_effects.conf

Consider only the file name part of the library path specified in
audio_effects.conf and only if the path contains "/lib/soundfx" then
try all standard paths in the folowing order: /odm/.. /vendor/.. and /system/..

Bug: 38000861
Test: check effect libraries are loaded from /system/lib or /vendor/lib
Change-Id: Ib02ecb3a464a59e7b7babcd9405b8fe4dc074745