Bluetooth: Controller: Fix Periodic Adv Report to scan max data length

Fix implementation to limit Periodic Advertising data to a
configurable maximum length when generating HCI reports.

Bluetooth Test Specification defines Scan_Max_Data value
in IXIT. When HCI LE Periodic Advertising Report events are
generated by assembling the chain PDUs, the test cases
expect that if the data length is no more than
Scan_Max_Data, then at least once the IUT shall not
truncate the data in the advertising report.

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