ARM: dts: msm: Add node for sdx ipc driver to communicate with AP

Add a node to sdx ipc driver to facilitate communication between
external AP and modem using IPC gpios. Modem is intimated of AP's
state based on gpio events and vice-versa.

Change-Id: Iab4ce5a952682b2d8e998bb38c2be43d9b47e0f9
Signed-off-by: Manohar Vavilapalli <mvavilap@codeaurora.org>