gpio: mcp23s08: fix up compilation error
gpio: mcp23s08: fix up compilation error

The driver depends on the chip.of_node being present to compile,
which is the case on some target platforms but not others.
Instead, rely on chip.dev->of_node to be used, as struct device
always has an of_node in place.

Cc: Alexander Stein <dbef83f64948dc68aad31596bbf6991154a9d730@systec-electronic.com>
Suggested-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>
Signed-off-by: Linus Walleij <9cd9d802d23c0ed5e224beabf4ae4a5c478746ef@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs