BLE: rename AdvertisingReportEvent::getAdvertisingData into getPayload.
BLE: rename AdvertisingReportEvent::getAdvertisingData into getPayload.

This change makes it consistent with PeriodicAdvertisingReportEvent.

andcor02/mbed-os,andcor02/mbed-os,andcor02/mbed-os,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed,mbedmicro/mbed,andcor02/mbed-os,kjbracey-arm/mbed,kjbracey-arm/mbed,kjbracey-arm/mbed,andcor02/mbed-os,mbedmicro/mbed,andcor02/mbed-os,mbedmicro/mbed