ARM: dts: msm: enable scatter gather etr-ddr mode on 9640

Scatter gather option for TMC ETR DDR mode supports the use of a table of
locations of 4K blocks of physical memory. Enable this feature to
facilitate users to increase the trace buffer size as long as DDR memory is
available in the system.

Change-Id: I6b0b090c25ea01acf3f455025fc4b1b8e1e7352b
Signed-off-by: Sarangdhar Joshi <spjoshi@codeaurora.org>