cpupower: add Makefile dependencies for install targets

commit fb7791e2 upstream.

This allows building cpupower in parallel rather than serially.

Signed-off-by: Ivan Babrou <ivan@cloudflare.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>