ARM: dts: msm: Enable rmtfs device for SDM670

It is needed to enable remote file system on modem processor, which
needs access to store data onto eMMC/UFS device.

The shared memory size used by modem and apps for this purpose is 2MB.

Change-Id: I5b7189ac260e2dcbb40a5d6b61b12b5255b500af
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>