soc: qcom: glink_ssr: Add kref for cb_data

The variable cb_data is accessed from parallel threads where one thread
can free it anytime, this creates use after free scenerio.

To avoid use after free cases cb_data is freed only when kref count
goes to zero.

CRs-Fixed: 2023620
Change-Id: I74225fc61f8ede03a40ff35d2b963d90c0d4689f
Signed-off-by: Dhoat Harpal <hdhoat@codeaurora.org>