ARM: dts: msm8974: Split efs in rfsa and rmtfs

One part of the efs memory region is used specifically for sharing file system
buffers between the apps and modem cpus (aka rmtfs), so better reflect this
split.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>