soc: qcom: glink: Initialize dummy xprt with dummy functions

Few function pointers are left uninitialized in dummy transport.
System can crash if these function pointer get dereferenced.

Initialize all the function pointers which can get called, with
dummy functions.

CRs-Fixed: 2067859
Change-Id: I9172776d9ffa0af5deb9898125fc6403fdcdee0f
Signed-off-by: Dhoat Harpal <hdhoat@codeaurora.org>