staging:iio:accel:sca3000 Tidy up probe order to avoid a race.

Previously the device was exposed to userspace and in kernel consumers
before the interrupts had been configured. As nothing stopped them being
enabled in the interval this could cause unhandled interrupts.

Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>