virt: vbox: Rename guest_caps struct members to set_guest_caps

Rename guest_caps[_tracker] struct members to set_guest_caps[_tracker]
this is a preparation patch for adding support for the
VBGL_IOCTL_GUEST_CAPS_ACQUIRE ioctl.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20200709120858.63928-4-hdegoede@redhat.com


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