virt: vbox: linux: fix all kernel-doc warnings

Use kernel-doc format for functions that are almost complete in their
kernel-doc comments.
For other functions, just change the comment to a common C comment.
This prevents 7 kernel-doc warnings.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20231222052521.14333-2-rdunlap@infradead.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>