ARM: dts: msm: Add IPCC self-ping node for testing

The DT node is configured in a loopback fashion for
MPROC protocol, such that the APPS would raise an
interrupt on itself making a roundtrip of the IPCC
hardware. This is useful for testing the IPCC driver.

Change-Id: I96fe510f0fad9d9d05def73fc68764893210d8f5
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>