Bluetooth: controller: split: Fix radio abort race condition

When aborting radio event, there is a possibility that the
packet timer would start the radio while the packet timer
is being reset. Hence, perform a second radio state disable
with packet timers uninitialised.

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

subsys/bluetooth/controller/ll_sw/nordic/lll/lll_scan.c

@@ -576,6 +576,9 @@ static void isr_abort(void *param)
 	ticker_stop(TICKER_INSTANCE_ID_CTLR, TICKER_USER_ID_LLL,
 		    TICKER_ID_SCAN_STOP, NULL, NULL);
 
+	/* Under race conditions, radio could get started while entering ISR */
+	radio_disable();
+
 	isr_cleanup(param);
 }