cpupower: Restore format of frequency-info limit

The intel_pstate kselftest expects that the output of
`cpupower frequency-info -l | tail -1 | awk ' { print $1 } '`
to get frequency limits.  This does not work after the following two
changes.

 - 562e5f1a: rework the "cpupower frequency-info" command
   (Jacob Tanenbaum) removed parsable limit output
 - ce512b84: Do not analyse offlined cpus
   (Thomas Renninger) added newline to break limit parsing more

This change preserves human readable output if wanted as well as
parsable output for scripts/tests.

Cc: Thomas Renninger <trenn@suse.com>
Cc: "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>