samples: sensor: dht_polling run sample on sensor present

Add a fixture to run the sample only when the DHT sensor
HX330x is present (shield) on the nucleo_f40re board
'fixture_i2c_hs300x'
The stm32f401 Nucleo board itself has no sensor mounted

Signed-off-by: Francois Ramu <francois.ramu@st.com>