Correction to manpage of cpupower

Manpage of cpupower is listing wrong sub-commands in "See Also"
section. The option for cpupower-idle(1) should actually be
cpupower-idle-info(1) and cpupower-idle-set(1). This patch corrects
this anomaly.

Signed-off-by: Brahadambal Srinivasan <latha@linux.vnet.ibm.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>