9pfs: drop Doxygen format from qemu_dirent_dup() API comment

9pfs: drop Doxygen format from qemu_dirent_dup() API comment

API doc comments in QEMU are supposed to be in kerneldoc format, so drop
occurrences of "@c" which is Doxygen format for fixed-width text.

Link: https://lore.kernel.org/qemu-devel/CAFEAcA89+ENOM6x19OEF53Kd2DWkhN5SN21Va0D7yepJSa3Jyg@mail.gmail.com/
Based-on: <E1nP9Oz-00043L-KJ@lizzy.crudebyte.com>
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <E1nPTwO-0006pl-Np@lizzy.crudebyte.com>