ppc64_cpu: add all parameter to --cores-on to online all cores
ppc64_cpu: add all parameter to --cores-on to online all cores

Rather than finding out how many cores are in a system, and then passing
that value to --cores-on, it can be handy to have a shortcut to just
online all cores.

Signed-off-by: Nishanth Aravamudan <32d5d7104760c6969dbcc939b04e64f225673f91@linux.vnet.ibm.com>

shenki/powerpc-utils,shenki/powerpc-utils,shenki/powerpc-utils