docs: ABI: vdso: use the right format for ABI

This ABI is not following the format described at ABI/README.

Use it, filling in the blanks with the git log that added it,
and using the current e-mail from Andy.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/28c7cf3a71e15fb7499b70ec8f38c2efaaf4add2.1604042072.git.mchehab+huawei@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: mchehab

Documentation/ABI/stable/vdso

@@ -1,3 +1,9 @@
+What:		vDSO
+Date:		July 2011
+KernelVersion:	3.0
+Contact:	Andy Lutomirski <luto@kernel.org>
+Description:
+
 On some architectures, when the kernel loads any userspace program it
 maps an ELF DSO into that program's address space.  This DSO is called
 the vDSO and it often contains useful and highly-optimized alternatives