Backport isVoiceCapable() using getPhoneType()

isVoiceCapable() was unhidden in API 22. We couldn't copy the code to
backport it because the app doesn't have access to
com.android.internal.R.bool.config_voice_capable. So we use getPhoneType()
as a workaround since it also calls isVoiceCapable().

Bug: 25629359

Change-Id: Ia117823ae871c7132014d10c5475eba5dbfda009