Documentation: core-api/cpu_hotplug: fix a typo

fourV CPUs should be four CPUs.
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Link: https://lore.kernel.org/r/20200904101902.29560-1-song.bao.hua@hisilicon.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/core-api/cpu_hotplug.rst

@@ -30,7 +30,7 @@ which didn't support these methods.
 Command Line Switches
 =====================
 ``maxcpus=n``
-  Restrict boot time CPUs to *n*. Say if you have fourV CPUs, using
+  Restrict boot time CPUs to *n*. Say if you have four CPUs, using
   ``maxcpus=2`` will only boot two. You can choose to bring the
   other CPUs later online.