drivers/sensor: iis2iclx: fix multi-instance using new helpers

This commit simplifies the Device Tree configuration by using
the new helpers introduced in #30536.

In particular:
    - get bus devices with DEVICE_DT_GET
    - get SPI information with SPI_CONFIG_DT_INST

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