libpayload: queue: Add a helper macro for checking singleton queue

Check if the simple queue consists of only 1 element.

BUG=b:24676003
BRANCH=None
TEST=Compiles successfully.

Change-Id: Ib257a5e6b9042b42c549f8ad8b943e3b75fd8c9c
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 5435d6fec1c4fbb4c04ba5b8c15caff9ee4e50f0
Original-Change-Id: I7a8cb9c4e7e71956e85e65b3e7b8e0af4d354110
Original-Signed-off-by: Furquan Shaikh <furquan@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/311256
Original-Commit-Ready: Furquan Shaikh <furquan@chromium.org>
Original-Tested-by: Furquan Shaikh <furquan@chromium.org>
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/12412
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins)
1 file changed