gpio: max732x: Be sure to clamp return value

gpio: max732x: Be sure to clamp return value

As we want gpio_chip .get() calls to be able to return negative
error codes and propagate to drivers, we need to go over all
drivers and make sure their return values are clamped to [0,1].
We do this by using the ret = !!(val) design pattern.

Also start to propagate the error code here as the end of the
series fixes this to work for all drivers.

Cc: Semen Protsenko <semen.protsenko@globallogic.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by:Nicholas Krause <xerofoify@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>