ARM: dts: msm: add sg-enable to tmc etr dt node

Add sg-enable to TMC ETR DT node to indicate that scatter gather feature is
supported with TMC ETR configuration. sg-enable DT entry will help enable
this feature only on those targets which support it.

Change-Id: Ic24ca1232912d9fa31282e65ff4a2642259711e6
Signed-off-by: Sarangdhar Joshi <spjoshi@codeaurora.org>