Some address/memory APIs have different type between
'hwaddr/target_ulong addr' and 'int len'. It is very unsafe, especially
some APIs will be passed a non-int len by caller which might cause
overflow quietly.
Below is an potential overflow case:
    dma_memory_read(uint32_t len)
      -> dma_memory_rw(uint32_t len)
        -> dma_memory_rw_relaxed(uint32_t len)
          -> address_space_rw(int len) # len overflow

CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Peter Crosthwaite <crosthwaite.peter@gmail.com>
CC: Richard Henderson <rth@twiddle.net>
CC: Peter Maydell <peter.maydell@linaro.org>
CC: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>