soc: qcom: add secure processor communication (spcom) driver

This driver supports communication with secure processor subsystem
(SPSS) over rpmsg and ungerlying glink transport layer. The
communication is based on using shared memory and interrupts.

Add snapshot for spcom driver from msm-4.14 commit cff38c326b98
("soc:qcom:spcom: free not consumed packet on rx timeout").

Change-Id: I28d704b18a3b0de9711ff3235c3f5551e7302557
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
Signed-off-by: Amir Samuelov <amirs@codeaurora.org>