defconfig: mdm: Enable IPC Router G-Link Transport

The IPC Router G-Link Transport permits IPC Router communication over
G-Link to the other processors in the SoC.

Change-Id: I2f5d6acfdb76e37d7bea9d785f9edba44a803dc1
Signed-off-by: Steven Cahail <scahail@codeaurora.org>