KVM: PPC: e500: fix allocation size error on g2h_tlb1_map

We were only allocating half the bytes we need, which was made more
obvious by a recent fix to the memset in  clear_tlb1_bitmap().

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Cc: stable@vger.kernel.org