drivers: spi: fix sample syntax

Upcoming versions of breathe highlight code embedded in Doxygen blocks.
In this case, the Devicetree fragment contained invalid syntax leading
to Sphinx warnings.

(cherry picked from commit be21b455228905ffe368513a70bfef8a3d7b85be)

Original-Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
GitOrigin-RevId: be21b455228905ffe368513a70bfef8a3d7b85be
Change-Id: Ic4a5594a0ca53960dd2885ec3eb88a84c0b72d67
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/3829405
Tested-by: CopyBot Service Account <copybot.service@gmail.com>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
1 file changed