Disable stubby PIN pad unless it's a small device.

The PIN pad now uses small keys in landscape mode (you can reach the
bouncer via the camera) so the PIN pad actually fits on screen. This CL
disables it for screens which have sufficient screen real-estate to show
the full PIN pad.

Example on small landscape screen:
https://screenshot.googleplex.com/4AtdnAxJqQscCKM

Example on large landscape screen:
https://screenshot.googleplex.com/9vH5Zwf9XRSM6fK

Test: Manually verified, see screenshots.
Bug: 197748884

Change-Id: I3f7699aa6a72f733c4b49b50ff0998cc9cd6f1d3