87f9fe3a

's intention was to not create properties that a subdevice
doesn't have configuration options for (i.e. if you have a pointer+keyboard
device, don't expose tapping configuration on the keyboard subdevice).

The result was messy, the checker function had a confusing triple-negation and
some properties weren't checked - e.g. left-handed was allowed for touch/tablet
but not for pointer, dwt was allowed for any device.

Fix this by moving the check into the property init function directly and
inverting the helper function to be easier to read.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>