ehci: switch to new-style memory ops

Also register different memory regions for capabilities,
operational registers and port status registers.  Create
separate tracepoints for operational regs and port status
regs.  Ditch a bunch of sanity checks because the memory
core will do this for us now.

Offloading the byte, word and dword access handling to the
memory core also has the side effect of fixing ehci register
access on bigendian hosts.

Cc: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
