PPC: e500: initialize GPRs as per epapr

ePAPR defines the initial values of cpu registers.
This patch initialize the GPRs as per ePAPR specification.

This resolves the issue of guest reboot/reset (guest hang on reboot).

Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
[agraf: add whitespace line]
Signed-off-by: Alexander Graf <agraf@suse.de>
