soc: qcom: hab: change the unregistration to be dummy

HAB service should be kept available as long as possible
since it is very fundamental. It can possibly be used in
the GVM(Guest Virtual Machine) shutdown procedure to
talk with the hypervisor. And the unregistration function
will only be left to give a log message.

Change-Id: I0cbc153a68a0fb496d14fc49db6cfee211a01722
Signed-off-by: Yong Ding <yongding@codeaurora.org>