iio: imu: st_lsm6dsx: always enter interrupt thread

The interrupt source can come from multiple sources,
fifo and wake interrupts.
Enter interrupt thread to check which interrupt that has fired.

Signed-off-by: Sean Nyekjaer <sean@geanix.com>
Reviewed-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>