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

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: I37bf8cc4bdbe3e7e9a7e7eb88883e95b8f168359
Signed-off-by: Xiaogang Cui <xiaogang@codeaurora.org>