Input: ad714x - read the interrupt status registers in a row

The interrupt status registers should be read in row to avoid invalid data.

Alter "read" method for both bus options to allow reading several registers
in a row and make sure we read interrupt status registers properly.

Read sequence saves 50% of bus transactions compared to single register
reads. So use it also for the result registers, which are also located
in a row.

Also update copyright notice.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>