msm_mpdecision: Re-enable as an optional hotplug driver

Lets re-enable mpdecision but keep intelli-plug as default, allowing users
to have a choice between the two.

Change-Id: I759a13eb6bbd97eb7bf7d23f6e2218868d2827d0
Signed-off-by: Rob Beane <robbeane@gmail.com>