ARM: dts: msm: Enable cache coherency for fastrpc devices on msmcobalt

Enabled cache coherency for fastrpc devices by adding dma-coherent
flag.

Change-Id: I8ea271103c202cefdedae62f2717f1bee44c1d78
Acked-by: Viswanatham Paduchuri <vpaduchu@qti.qualcomm.com>
Signed-off-by: Sathish Ambley <sathishambley@codeaurora.org>