ANDROID: dm: android-verity: 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>

[AmitP: Folded following android-4.9 commit changes into this patch
        7e70218c2699 ("ANDROID: dm: Minor cleanup")
        67584ff8412b ("ANDROID: dm: rename dm-linear methods for dm-android-verity")]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>