phb5: Enable Gen5
phb5: Enable Gen5

Registers for Gen5 have been initialized in a previous patch. So let's
activate it!

Signed-off-by: Michael Neuling <7b0ab45a730e48a69239010b5b8fe5fa4e8eaac6@neuling.org>
Signed-off-by: Vasant Hegde <a6d753843573f7bfed5075c1e875b0be8007a0ab@linux.vnet.ibm.com>

open-power/skiboot,open-power/skiboot,legoater/skiboot,shenki/skiboot,open-power/skiboot,shenki/skiboot,qemu/skiboot,qemu/skiboot,open-power/skiboot,legoater/skiboot,qemu/skiboot,qemu/skiboot,legoater/skiboot,open-power/skiboot,legoater/skiboot,legoater/skiboot,shenki/skiboot,qemu/skiboot,shenki/skiboot,shenki/skiboot