hal: avoid resetting to speaker if HDMI is still connected

Burst of sound is perceived over speaker during song switch, and the
cause is that APM closeOutput triggers resetting device to speaker when
playback ends.

Resetting to speaker is intended only when HDMI is unplugged, so we need
to avoid doing so if HDMI is still connected.

Change-Id: I32bb809ea037f7f180d613cacacc7e3b0210d91c
CRs-Fixed: 997689