tests: build_all/sensor: add hts221 spi test

1. Add hts221 test in spi.dtsi
2. I2C test was disabled in app.overlay for few sensors for which
   multi-instance was not working very long time ago. Now there
   is no reason for not running the tests, so delete the skipping
   rule.

Signed-off-by: Armando Visconti <armando.visconti@st.com>