[nrf fromlist] samples: Bluetooth: use correct periodic advertising intervals

BT_GAP_ADV_SLOW_INT_MIN and BT_GAP_ADV_SLOW_INT_MAX represent 1s and 1.2s, respectively,
in the extended advertising context, where the bit interval is 0.625 ms. Using them for
periodic advertising will result in a range of [2s, 2.4s], as the bit interval
for periodic advertising is 1.25ms.

Instead, BT_GAP_PER_ADV_SLOW_INT_MIN and BT_GAP_PER_ADV_SLOW_INT_MAX should be used in
this sample, and the range will become [1s, 1.2s].

Upstream PR: zephyrproject-rtos/zephyr#73418

Signed-off-by: Yuxuan Cai <yuxuan.cai@nordicsemi.no>
(cherry picked from commit dd4f7c3)

Author: yuxCai

samples/bluetooth/direction_finding_connectionless_tx/src/main.c

@@ -42,8 +42,8 @@ static struct bt_le_ext_adv_start_param ext_adv_start_param = {
 };
 
 static struct bt_le_per_adv_param per_adv_param = {
-	.interval_min = BT_GAP_ADV_SLOW_INT_MIN,
-	.interval_max = BT_GAP_ADV_SLOW_INT_MAX,
+	.interval_min = BT_GAP_PER_ADV_SLOW_INT_MIN,
+	.interval_max = BT_GAP_PER_ADV_SLOW_INT_MAX,
 	.options = BT_LE_ADV_OPT_USE_TX_POWER,
 };