kvm: remove dead code

The function kvm_io_bus_read_cookie is defined but never used
in current in-tree code.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --cc include/linux/kvm_host.h
Simple merge

diff --cc virt/kvm/kvm_main.c
Simple merge