KVM: PPC: BOOKEHV: rename e500hv_spr to bookehv_spr

This are not specific to e500hv but applicable for bookehv
(As per comment from Scott Wood on my patch
"kvm: ppc: bookehv: Added wrapper macros for shadow registers")

Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>