Smaller palm filtering width along top edge

If palm filtering is enabled on the top edge, this CL reduces the
default filtering width, which can now be different from the width along
the sides.

BUG=None
TEST=Deploy to device and check that pinch detection and palm rejection
are good. Also, create touchtest regression test for previously bad
pinch detection along the top edge.

Change-Id: I58735f280a09646978e7f345e3008990cb1feaf1
Reviewed-on: https://chromium-review.googlesource.com/724184
Commit-Ready: Sean O'Brien <seobrien@chromium.org>
Tested-by: Sean O'Brien <seobrien@chromium.org>
Reviewed-by: Andrew de los Reyes <adlr@chromium.org>
2 files changed