test: avoid erroneous devices to be passed into the test suites

test: avoid erroneous devices to be passed into the test suites

The litest features overlap with the litest device specifiers, so it's easy to
pass in LITEST_MOUSE where LITEST_POINTER should be passed in, and vice versa.
Lacking proper type checking the best we can do here is simply move the
devices into the negative range and check for that.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>