memory: s/dirty/clean/ in cpu_physical_memory_is_dirty()

All uses except one really want the other meaning.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Orit Wasserman <owasserm@redhat.com>
diff --git a/cputlb.c b/cputlb.c
index ec21405..eab91d7 100644
--- a/cputlb.c
+++ b/cputlb.c
@@ -284,7 +284,8 @@
             /* Write access calls the I/O callback.  */
             te->addr_write = address | TLB_MMIO;
         } else if (memory_region_is_ram(section->mr)
-                   && !cpu_physical_memory_is_dirty(section->mr->ram_addr + xlat)) {
+                   && cpu_physical_memory_is_clean(section->mr->ram_addr
+                                                   + xlat)) {
             te->addr_write = address | TLB_NOTDIRTY;
         } else {
             te->addr_write = address;