drivers/sensor/st: Fix wrong data byte swap for be

A 16-bit value built using byte shifts and ORs from a given
couple of lsb and msb bytes will result to be the same on both
little-endian and big-endian architectures, e.g.

    uint8_t lsb, msb;
    int16_t val;

    /* val is the same number on both le and be archs, but has
       different layout in memory */
    val = (msb << 8) | lsb;

All the xyz_raw_get() APIs of stmemsc sensor module build the sensor
data using the above method and DO NOT hence require (it actually leads
to wrong values on big-endian machines) to use any le/be swap routines,
such as sys_le16_to_cpu().

Fix #75758

Signed-off-by: Armando Visconti <armando.visconti@st.com>
(cherry picked from commit 9ea4cb96)