staging:iio:adc:ad7150: Add support for the second interrupt strobe.

The AD7150 features two outputs that can be used as interrupt strobes
to the host processor. In order to receive all events independently,
both need to utilized.

Update copyright notice.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>