samples: sensor: lps22hh: replace platform filter with fixture

Remove reference to a specific board, since that board doesn't have
this sensor.

Add a dependency on presence of a devicetree node that will be
required to build the driver.

Add a fixture that identifies the specific sensor required to run the
sample.  This should be added as a side effect of specifying the
shield (though this is not currently done, it must be added in the
device description).

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>