dt-bindings: at24: fix formatting and style

Make formatting and style consistent for the entire document.

This patch doesn't change the content of the binding.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Rob Herring <robh@kernel.org>