Bluetooth: controller: Revert strict preempt ticker start failure check

Revert the strict preempt ticker start failure check.
Preempt ticker start can fail when enqueuing prepares into
already filled pipeline which has preempt ticker already
started for the first prepare that was added in the
pipeline.

Regression introduced in commit 5b75bdf ("Bluetooth:
controller: nRF5: Check preempt event on timeout").

Fixes zephyrproject-rtos#35476.

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

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

@@ -71,7 +71,6 @@ static void isr_race(void *param);
 #if !defined(CONFIG_BT_CTLR_LOW_LAT)
 static void ticker_stop_op_cb(uint32_t status, void *param);
 static void ticker_start_op_cb(uint32_t status, void *param);
-static void ticker_start_next_op_cb(uint32_t status, void *param);
 static uint32_t preempt_ticker_start(struct lll_event *event,
 				     ticker_op_func op_cb);
 static void preempt_ticker_cb(uint32_t ticks_at_expire, uint32_t remainder,
@@ -644,6 +643,7 @@ int lll_prepare_resolve(lll_is_abort_cb_t is_abort_cb, lll_abort_cb_t abort_cb,
 
 		ret  = preempt_ticker_start(next, ticker_start_op_cb);
 		LL_ASSERT((ret == TICKER_STATUS_SUCCESS) ||
+			  (ret == TICKER_STATUS_FAILURE) ||
 			  (ret == TICKER_STATUS_BUSY));
 
 #else /* CONFIG_BT_CTLR_LOW_LAT */
@@ -710,8 +710,9 @@ int lll_prepare_resolve(lll_is_abort_cb_t is_abort_cb, lll_abort_cb_t abort_cb,
 	} while (p->is_aborted || p->is_resume);
 
 	/* Start the preempt timeout */
-	ret = preempt_ticker_start(p, ticker_start_next_op_cb);
+	ret = preempt_ticker_start(p, ticker_start_op_cb);
 	LL_ASSERT((ret == TICKER_STATUS_SUCCESS) ||
+		  (ret == TICKER_STATUS_FAILURE) ||
 		  (ret == TICKER_STATUS_BUSY));
 #endif /* !CONFIG_BT_CTLR_LOW_LAT */
 
@@ -758,13 +759,6 @@ static void ticker_start_op_cb(uint32_t status, void *param)
 		  (status == TICKER_STATUS_FAILURE));
 }
 
-static void ticker_start_next_op_cb(uint32_t status, void *param)
-{
-	ARG_UNUSED(param);
-
-	LL_ASSERT(status == TICKER_STATUS_SUCCESS);
-}
-
 static uint32_t preempt_ticker_start(struct lll_event *event,
 				     ticker_op_func op_cb)
 {
@@ -845,8 +839,9 @@ static void preempt(void *param)
 		uint32_t ret;
 
 		/* Start the preempt timeout */
-		ret = preempt_ticker_start(next, ticker_start_next_op_cb);
+		ret = preempt_ticker_start(next, ticker_start_op_cb);
 		LL_ASSERT((ret == TICKER_STATUS_SUCCESS) ||
+			  (ret == TICKER_STATUS_FAILURE) ||
 			  (ret == TICKER_STATUS_BUSY));
 
 		return;