iio: sx9310: Use irq trigger flags from firmware

We shouldn't need to set default irq trigger flags here as the firmware
should have properly indicated the trigger type, i.e. level low, in the
DT or ACPI tables.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Daniel Campello <campello@chromium.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>