Fix test_util_adapter_wrapper to use provided MTU in SD > 3 (#184)

Author: kenr

test/util/src/test_util_adapter_wrapper.cpp

@@ -903,9 +903,10 @@ void AdapterWrapper::setupScratchpad(const uint16_t mtu)
     scratchpad.common_opt.conn_bw.conn_bw.conn_bw_rx = BLE_CONN_BW_HIGH;
     scratchpad.common_opt.conn_bw.conn_bw.conn_bw_tx = BLE_CONN_BW_HIGH;
     scratchpad.opt.common_opt                        = scratchpad.common_opt;
-    scratchpad.mtu                                   = mtu == 0 ? DEFAULT_MTU_SIZE : mtu;
 #endif
 
+    scratchpad.mtu                                   = mtu == 0 ? DEFAULT_MTU_SIZE : mtu;
+
 #if NRF_SD_BLE_API == 3
     scratchpad.ble_enable_params.gatt_enable_params.att_mtu = scratchpad.mtu;
 #endif