cpupower: Remove absent 'v' parameter from monitor man page

Remove not supported '-v' parameter from the cpupower's 'monitor'
command description.
There is a '-v' parameter described in cpupower's 'monitor' command man
page. It isn't supported at the moment, and perhaps has never been
supported. When I run the monitor with this parameter I get the
following:

$ sudo LD_LIBRARY_PATH=lib64/ bin/cpupower monitor -v
monitor: invalid option -- 'v'
invalid or unknown argument
$ sudo LD_LIBRARY_PATH=lib64/ bin/cpupower monitor -V
monitor: invalid option -- 'V'
invalid or unknown argument

Signed-off-by: Roman Storozhenko <romeusmeister@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>