Added some info regarding petitboot.

Signed-off-by: Fernando Seiti Furusato <ferseiti@br.ibm.com>
Added instructions for powerKVM installation.

Signed-off-by: Fernando Seiti Furusato <ferseiti@br.ibm.com>
Merge pull request #1 from ferseiti/master

Ferseiti's section about petitboot and powerKVM installation