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

This driver supports communication with secure processor subsystem
over glink transport layer.
The communication is based on using shared memory and interrupts.
This driver exposes interface to both kernel and user space.

Change-Id: Iec5fc78c8370002643b549e43015c06b09d8ab8b
Signed-off-by: Amir Samuelov <amirs@codeaurora.org>