Bluetooth: use inclusive language to describe CPB

This patch replaces some non-inclusive terms based on the appropriate
language mapping table compiled by the Bluetooth SIG:
https://specificationrefs.bluetooth.com/language-mapping/Appropriate_Language_Mapping_Table.pdf



Specifically, these terms are replaced when describing the
connectionless peripheral broadcast feature:
master -> central
slave  -> peripheral

Signed-off-by: Archie Pusaka <apusaka@chromium.org>
Reviewed-by: Miao-chen Chou <mcchou@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>