soc: qcom: glink: Add null pointer guards in glink transports

A null pointer dereference was possible because a check on
the return value from kmalloc was not in place. This change
adds a null pointer check. This change also changes an
existing null check to check the correct pointer.

CRs-Fixed: 964856
Change-Id: I899b908b84d5d3b8e39b1b30b942e9eb7ed7f7da
Signed-off-by: Chris Lew <clew@codeaurora.org>