Ensure split-screen support isn't reported on devices with small displays.

Several partners with devices that have small displays have run into
issues w/ CTS-on-GSI testing as these builds hardcode support for
split-screen. This prevents split-screen from being reported as
supported if the display isn't compatible according to the CDD.

Bug: 158310372
Test: android.server.wm.SplitScreenTests#testMinimumDeviceSize()

Change-Id: I0dfd6caca5116dccc115d64b755998171abe831f