binder: update low_latency selection for binder transactions

The change limits the low_latency flag selection to binder
transactions of the foreground high priority tasks.

Change-Id: Id191e63ba2ccf5537cb45711c20bc22831129a18
Signed-off-by: Kishore Sri venkata Ganesh Bolisetty <bsrivenk@codeaurora.org>