Bluetooth: Controller: Fix per sync cancel and sync establ synchronize

Current implementation of ll_sync_create_cancel does not allow to stop
synchronization after ull_sync_setup is called. When that is done,
sync->timeout_reload is not zero and the ll_sync_create_cancel will
return BT_HCI_ERR_CMD_DISALLOWED. That means the Controller is able to
cancel periodic advertising synchronization only in period between
call to ll_sync_create and reception of AUX_ADV_IND that has SyncInfo
field.

The Controller should be able to cancell synchronization until first
AUX_SYNC_IND PDU is received and host notified about synchronization
established.

Complete information about synchronization status is provdied by two
ll_sync_set members: node_rx_sync_established and timeout_reload.
These two members of the structure were used in ll_sync_create_cancel
function to do a proper cancel and cleanup.
The node_rx_sync_established member was not cleared when sync was
established or expired. That was required to get a proper information
about synchronization state.

Besides that, to avoid race condition between ll_sync_create_cancel
and ull_sync_established_report, the latter function was extended
to check if cancel operation or sync lost has happened.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>