iio: accel: kxsd9: Fix scaling bug

commit 307fe9dd11ae44d4f8881ee449a7cbac36e1f5de upstream.

All the scaling of the KXSD9 involves multiplication with a
fraction number < 1.

However the scaling value returned from IIO_INFO_SCALE was
unpredictable as only the micros of the value was assigned, and
not the integer part, resulting in scaling like this:

$cat in_accel_scale
-1057462640.011978

Fix this by assigning zero to the integer part.

Tested-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>