Fix a pointer cast warning in the SIS DRM code.
This was introduced in patch 
ce65a44de07f73ceda1749812b75086b7add408d.
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>
        if (req.size == 0)
                return NULL;
        else
-               return (void *)~req.offset;
+               return (void *)(unsigned long)~req.offset;
 }
 
 static void sis_sman_mm_free(void *private, void *ref)