dts: bindings: Preserve newlines in descriptions

With https://github.com/zephyrproject-rtos/zephyr/pull/20185, multi-line
descriptions will be formatted nicely, but using '>' breaks it, because
it removes internal newlines (including between paragraphs).

See https://yaml-multiline.info/

.

Replace 'description: >' with 'description: |' to encourage '|'. That'll
prevent '>' from getting copied around and messing up long descriptions.

This will lead to some extra newlines in the output, but it's fine.
Line-wrapping messes up any manual formatting.

The replacement was done with

    $ git ls-files 'dts/bindings/*.yaml' | \
          xargs sed -i 's/description:\s*>/description: |/'

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>