dt-bindings: soc: qcom: Rename GLINK mbox transport to SPSS

Change the GLINK mbox transport to GLINK SPSS to avoid confusion with
the common mailbox framework. Rename the file from glink_probe to
glink-probe to match naming conventions.

Change-Id: Id406de79e216649fc36497307c332ce13104db36
Signed-off-by: Chris Lew <clew@codeaurora.org>