exec.c: replace hwaddr with uint64_t for better understanding

Function phys_page_set() and phys_page_set_level() 's argument *nb*
stands for number of pages to set instead of hardware address.

This would be more proper to use uint64_t instead of hwaddr for its
type.
Signed-off-by: NWei Yang <richardw.yang@linux.intel.com>
Message-Id: <20190321082555.21118-2-richardw.yang@linux.intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

exec.c

@@ -255,7 +255,7 @@ static uint32_t phys_map_node_alloc(PhysPageMap *map, bool leaf)
 }
 
 static void phys_page_set_level(PhysPageMap *map, PhysPageEntry *lp,
-                                hwaddr *index, hwaddr *nb, uint16_t leaf,
+                                hwaddr *index, uint64_t *nb, uint16_t leaf,
                                 int level)
 {
     PhysPageEntry *p;
@@ -281,7 +281,7 @@ static void phys_page_set_level(PhysPageMap *map, PhysPageEntry *lp,
 }
 
 static void phys_page_set(AddressSpaceDispatch *d,
-                          hwaddr index, hwaddr nb,
+                          hwaddr index, uint64_t nb,
                           uint16_t leaf)
 {
     /* Wildly overreserve - it doesn't matter much. */