move QEMUSGList typedef

Move the QEMUSGList typedef to qemu-common so it can easily be used.
The actual struct definition stays in dma.h.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/dma.h b/dma.h
index 3d8324b..a6db5ba 100644
--- a/dma.h
+++ b/dma.h
@@ -20,12 +20,12 @@
     target_phys_addr_t len;
 } ScatterGatherEntry;
 
-typedef struct {
+struct QEMUSGList {
     ScatterGatherEntry *sg;
     int nsg;
     int nalloc;
     target_phys_addr_t size;
-} QEMUSGList;
+};
 
 void qemu_sglist_init(QEMUSGList *qsg, int alloc_hint);
 void qemu_sglist_add(QEMUSGList *qsg, target_phys_addr_t base,