defconfig:sa8150: Enable RPMSG GLINK spi transport

The RPMSG GLINK spi transport enables communication to the wdsp
processor over a spi bus. The glink spi driver receives notifications
about processor status from a component manager and internally handles
SSR.

Change-Id: I92e96399f61c257df3f807b4010122c94f2d5f45
Signed-off-by: Hans Chang <hansc@codeaurora.org>