arm64: defconfig: Enable G-Link

G-Link is a generic link-layer transport similar to SMD that supports a
plug-in layer for the physical transport. This allows it to adapt to
different physical transports such as shared memory, UARTs, buses and DMA.

CRs-Fixed: 1059650
Change-Id: I5445d7ed43de40dceb623be87158da67918d9b3a
Signed-off-by: Chris Lew <clew@codeaurora.org>