bluetooth: support setting RSSI test limits per fixture

This patch supports setting RSSI test limits per fixture.

BUG=chrome-os-partner:47419
TEST=manually tested.

Change-Id: I482850db1b246e998c5cb251353ae9dd8622d587
Reviewed-on: https://chromium-review.googlesource.com/311956
Commit-Ready: Shyh-In Hwang <josephsih@chromium.org>
Tested-by: Shyh-In Hwang <josephsih@chromium.org>
Reviewed-by: Pin-chih Lin <johnylin@chromium.org>
1 file changed