Documentation: devicetree: Fix max77693 spelling errors

This patch corrects spelling errors in the max77693 devicetree doc,
in particular example code containing typos.

Signed-off-by: Sebastiaan Schalbroeck <schalbroeck@gmail.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Rob Herring <robh@kernel.org>