drivers/sensor: lis2dux12: fix mode when setting odr

In lis2dux12_set_odr(), the call to stmemsc module lis2dux12_mode_set()
API is done with the .fs field left uninitialized, so setting the
underlying device regs in an unproper way.

Suggested-by: Luis Ubieda <luisf@croxel.com>
Signed-off-by: Armando Visconti <armando.visconti@st.com>
(cherry picked from commit 8bc00e14)