hw: hyperv: vmbus: Fix 32bit compilation

Fix 32-bit build error for vmbus:

  hw/hyperv/vmbus.c: In function ‘gpadl_iter_io’:
  hw/hyperv/vmbus.c:383:13: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
  383 |         p = (void *)(((uintptr_t)iter->map & TARGET_PAGE_MASK) | off_in_page);
      |             ^
  cc1: all warnings being treated as errors

Fixes: 0d71f7082d7 ("vmbus: vmbus implementation")
Signed-off-by: Jon Doron <arilou@gmail.com>
Tested-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Reviewed-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Message-Id: <20200715084326.678715-3-arilou@gmail.com>
[lv: updated with commit description from <20200906050113.2783642-1-richard.henderson@linaro.org>]
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

hw/hyperv/vmbus.c

@@ -380,7 +380,8 @@ static ssize_t gpadl_iter_io(GpadlIter *iter, void *buf, uint32_t len)
             }
         }
 
-        p = (void *)(((uintptr_t)iter->map & TARGET_PAGE_MASK) | off_in_page);
+        p = (void *)(uintptr_t)(((uintptr_t)iter->map & TARGET_PAGE_MASK) |
+                off_in_page);
         if (iter->dir == DMA_DIRECTION_FROM_DEVICE) {
             memcpy(p, buf, cplen);
         } else {