iio: accel: st_accel: Fix invalid mount_matrix on devices without ACPI _ONT method

When apply_acpi_orientation() fails, st_accel_common_probe() will fall back
to iio_read_mount_matrix(), which checks for a mount-matrix device property
and if that is not set falls back to the identity matrix.

But when a sensor has no ACPI companion fwnode, or when the ACPI fwnode
does not have a "_ONT" method apply_acpi_orientation() was returning 0,
causing iio_read_mount_matrix() to never get called resulting in an
invalid mount_matrix:

[root@fedora ~]# cat /sys/bus/iio/devices/iio\:device0/mount_matrix
(null), (null), (null); (null), (null), (null); (null), (null), (null)

Fix this by making apply_acpi_orientation() always return an error when
it did not set the mount_matrix.

Fixes: 3d8ad94b

 ("iio: accel: st_sensors: Support generic mounting matrix")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Marius Hoch <mail@mariushoch.de>
Link: https://lore.kernel.org/r/20230416212409.310936-1-hdegoede@redhat.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>