page migration: fix wrong comment in address_space_operations.migratepage()

There is no parameter "sync" in address_space_operations->migratepage().
It should be migrate_mode.  And the comment is for MIGRATE_ASYNC.

Signed-off-by: Tang Chen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
1 file changed