Documentation: ioctl: document 0x07 ioctl code

It looks like this was supposed to be documented when VSOCK was
added[1], but it got lost in later submissions.

Link: https://lore.kernel.org/20130109000024.3719.71468.stgit@promb-2n-dhcp175.eng.vmware.com/#Z31Documentation:ioctl:ioctl-number.txt

 [1]
Fixes: d021c344 ("VSOCK: Introduce VM Sockets")
Signed-off-by: Alyssa Ross <hi@alyssa.is>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240725171120.12226-2-hi@alyssa.is