The dma related variable dma.dst/src/cnt is dma_addr_t, it is
uint64_t in x64 platform. Change these usage from uint32_to
uint64_t to avoid trancation in edu_dma_timer.

Signed-off-by: Li Qiang <liq3ea@163.com>
Message-Id: <20190510164349.81507-4-liq3ea@163.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>