iio: imu: st_lsm6dsx: flip irq return logic

commit ec76d918 upstream

No need for using reverse logic in the irq return,
fix this by flip things around.

Signed-off-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>