x86: add power management line in /proc/cpuinfo

Change /proc/cpuinfo on 32-bit, it will look like on 64-bit.
'power management' line is added and power management information
will be printed at the line.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>