Bluetooth: Controller: Restrict AD Data to BT_CTLR_ADV_DATA_LEN_MAX

Strictly restrict AD Data length to BT_CTLR_ADV_DATA_LEN_MAX
when there can be free bytes in Advertising PDU with common
extended header format of less that the maximum 64 bytes.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>