The adis_enable_irq() does a read & a write. This change keeps a lock for
the duration of both operations vs for each op.

The change is also needed in adis16480, since that has it's own
implementation for adis_enable_irq().
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>