ARM: dts: msm: Add ipc-spinlock entry for msmgold

Add the ipc-spinlock entry to facilitate locking between apps and
non-apps processors.

Change-Id: Id2fce40f490371cf8c12713ebc43eec2b8a9f71c
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>