staging: dgnc: Fix Kconfig help header and text

Replace Kconfig help header and text to match other modules. Issue found
by checkpatch.

Spacing adjusted to match Documentation/process/coding-style.rst. Issue
reported by rdunlap@infradead.org.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Sehro Rautenkranz <sehro@sehro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>