audioflinger: effect: fix deadlock after dumpsys

Bug: 268441977
Test: add a device effect, call dumpsys twice, proxy is marked as "might
be deadlocked"

This CL fixes lock/unlock on the wrong lock

Change-Id: I6923e891a0d87a1be87edbaf44baa554ee729adb
Signed-off-by: François Gaffie <francois.gaffie@renault.com>