Revert "sensors: hts221: provide name to Kconfig choice"

This reverts commit 2a7efb74.

"choice" section in board Kconfig.defconfig introduces a dependency
from the sensor to the board. As a consequence a warning was generated
whenever the sensor was used on another board.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>