Replace the BT_CTLR_ADVANCED_SCHEDULING_CENTRAL_CONN_SPACING
Kconfig with BT_CTLR_CENTRAL_SPACING to configure the
the spacing from the beginning of a central connection event
to beginning of the next central connection when supporting
multiple simulataneous central connections.
If the BT_CTLR_CENTRAL_SPACING in microseconds is smaller
then the required time reservation for a connection event,
for given maximum data length and PHY in use, then the
calculated time reservation will be used as the spacing
between consecution central connection events.
The change fixes an issue wherein use of old Kconfig with
higher values causes new central connections to be placed
in between already connected central role if there was
free time space available to fit the new connections time
reservation.
Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>