iio: imu: st_lsm6dsx: move wakeup event enable mask to event_src

iio: imu: st_lsm6dsx: move wakeup event enable mask to event_src

The mask value being assigned to the irq1_func and irq2_func fields of the
irq_config struct is specific to a single event source (i.e. the wakeup
event), and as such it should be separate from the definition of the
interrupt function registers, which cover multiple event sources.
In preparation for adding support for more event types, change the
irq1_func and irq2_func type from an {address, mask} pair to an address,
and move the mask value to a new field of struct st_lsm6dsx_event_src. No
functional changes.

Signed-off-by: Francesco Lavra <flavra@baylibre.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>