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

Documentation/userspace-api/ioctl/ioctl-number.rst

@@ -78,6 +78,7 @@ Code  Seq#    Include File                                           Comments
 0x03  all    linux/hdreg.h
 0x04  D2-DC  linux/umsdos_fs.h                                       Dead since 2.6.11, but don't reuse these.
 0x06  all    linux/lp.h
+0x07  9F-D0  linux/vmw_vmci_defs.h, uapi/linux/vm_sockets.h
 0x09  all    linux/raid/md_u.h
 0x10  00-0F  drivers/char/s390/vmcp.h
 0x10  10-1F  arch/s390/include/uapi/sclp_ctl.h