mhi: core: unlink MHI device from MHI chan during device release

During MHI shutdown, we destroy all MHI devices that are tied to
MHI controller. During that process we unbind drivers from devices
if there is a register driver. In same function we unlink MHI
device from MHI channel. Since, not all devices have a registered
driver unlinking does not occur. If unlinking does not occur, we
do not create new devices during next power up sequence. Move
unlinking to release function to guarantee unlink always occur
during MHI shutdown.

CRs-Fixed: 2323691
Change-Id: I00b2761d1cc8015f5634242c669a5844be2d9c83
Acked-by: Bhaumik Vasav Bhatt <bbhatt@qti.qualcomm.com>
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>