ANDROID: dm: Mounting root as linear device when verity disabled

This CL makes android-verity target to be added as linear
dm device if when bootloader is unlocked and verity is disabled.

Bug: 27175947
Change-Id: Ic41ca4b8908fb2777263799cf3a3e25934d70f18
Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>