soc: qcom: glink: Move channel to dummy xprt with lock

In core_channel_cleanup function channel is moved to dummy xprt
without taking channel lock. This leads to race condition where
transport poniter is pointing to dummy but channel still belong
to old transport.

Channel is moved to dummy with channel lock.

CRs-Fixed: 2005731
Change-Id: I91903140c1bfa29d909847f318d1339bb717fffc
Signed-off-by: Dhoat Harpal <hdhoat@codeaurora.org>