memory: change dirty setting APIs to take a size

Instead of each target knowing or guessing the guest page size,
just pass the desired size of dirtied memory area.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/arch_init.c b/arch_init.c
index 95ac682..2366511 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -285,7 +285,7 @@
             for (addr = 0; addr < block->length; addr += TARGET_PAGE_SIZE) {
                 if (!memory_region_get_dirty(block->mr, addr,
                                              DIRTY_MEMORY_MIGRATION)) {
-                    memory_region_set_dirty(block->mr, addr);
+                    memory_region_set_dirty(block->mr, addr, TARGET_PAGE_SIZE);
                 }
             }
         }