caps: Additional ppc64 hardware information

Includes extra information (manufacturer and product name) about ppc64
hosts in the getVdsHardwareInfo command. This extra information is
obtained from the device tree and skipped in case it is missing.

Change-Id: I8f67a830740b64bc246f680f2c7a18a4293f4cc2
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1149262
Signed-off-by: Vitor de Lima <vdelima@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/33857
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>