BugLink: https://launchpad.net/bugs/1644726

This patch adds support for the AD5592R (spi) and AD5593R (i2c)
ADC/DAC/GPIO devices.
Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
(backported from commit 56ca9db8)
Signed-off-by: Shrirang Bagul <shrirang.bagul@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>