DMA_transfer_handler is actually an ISA thing, and as such has no
business in qemu-common.h.  Move it to hw/isa/isa.h, and rename it to
IsaDmaTransferHandler.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>