Bluetooth: Controller: Kconfig to permit periodic sync event skip

When AUX_ADV_IND or AUX_CHAIN_IND auxiliary channel PDU scan
radio event overlaps Periodic Sync radio event in unreserved
time space, let the Periodic Sync radio event be aborted so
that the auxiliary channel PDU can be received to generate
Extended Advertising Reports. Added a new Kconfig to enable
this.

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