fix(usb_host_uac): build failure if no mic/spk channel

Author: Schuwi

components/usb/usb_device_uac/usb_device_uac.c

@@ -505,8 +505,12 @@ esp_err_t uac_device_init(uac_device_config_t *config)
     s_uac_device->spk_itf_num = config->spk_itf_num;
     s_uac_device->mic_itf_num = config->mic_itf_num;
 #else
+#if CFG_TUD_AUDIO_FUNC_1_N_CHANNELS_RX
     s_uac_device->spk_itf_num = ITF_NUM_AUDIO_STREAMING_SPK;
+#endif
+#if CFG_TUD_AUDIO_FUNC_1_N_CHANNELS_TX
     s_uac_device->mic_itf_num = ITF_NUM_AUDIO_STREAMING_MIC;
+#endif
 #endif
 
     BaseType_t ret_val;