Remove IO_MEM_SUBPAGE

Replace with a MemoryRegion flag.

Signed-off-by: Avi Kivity <avi@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
diff --git a/memory.c b/memory.c
index 25b36ff..24b6b6f 100644
--- a/memory.c
+++ b/memory.c
@@ -862,6 +862,7 @@
     }
     mr->addr = 0;
     mr->offset = 0;
+    mr->subpage = false;
     mr->enabled = true;
     mr->terminates = false;
     mr->ram = false;