iio: humidity: hts221: remove warnings in hts221_parse_{temp,rh}_caldata()

Remove following sparse warnings in hts221_parse_temp_caldata() and in
hts221_parse_rh_caldata():
drivers/iio/humidity/hts221_core.c:302:19: warning: cast to
restricted __le16
drivers/iio/humidity/hts221_core.c:314:18: warning: cast to
restricted __le16
drivers/iio/humidity/hts221_core.c:320:18: warning: cast to
restricted __le16
drivers/iio/humidity/hts221_core.c:355:18: warning: cast to
restricted __le16
drivers/iio/humidity/hts221_core.c:361:18: warning: cast to
restricted __le16

Fixes: e4a70e3e ("iio: humidity: add support to hts221 rh/temp combo device")

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>