audiopolicy: fix ring stream volume cannot apply when previewing ringtone

Using AUDIO_DEVICE_OUT_SPEAKER to replace AUDIO_DEVICE_OUT_SPEAKER_SAFE
for device match.

Bug: 129456342
Test: volume can adjust while previewing ringtone
Change-Id: I3015f811ac6d2e3f3cdd606f453348c4bc526935
Signed-off-by: Robert Lee <lerobert@google.com>