pcpu_sync_sleep monitor "uint64_t sync" change to "1UL << mask_bit",
which is not very clear to take use of it.
change it to wait_sync_change, means monitor "uint64_t sync" change to
"wake_sync", make the function clear to use.
And expose it for the usage of the following patches.
Signed-off-by: Jason Chen CJ <jason.cj.chen@intel.com>