Split TLB addend and target_phys_addr_t

Historically the qemu tlb "addend" field was used for both RAM and IO accesses,
so needed to be able to hold both host addresses (unsigned long) and guest
physical addresses (target_phys_addr_t).  However since the introduction of
the iotlb field it has only been used for RAM accesses.

This means we can change the type of addend to unsigned long, and remove
associated hacks in the big-endian TCG backends.

We can also remove the host dependence from target_phys_addr_t.

Signed-off-by: Paul Brook <paul@codesourcery.com>
