Fix a compilation error if Bluetooth not enabled (espressif#2172)

Author: ahornerr

cores/esp32/esp32-hal-misc.c

@@ -21,7 +21,9 @@
 #include "esp_partition.h"
 #include "esp_log.h"
 #include "esp_timer.h"
+#ifdef CONFIG_BT_ENABLED
 #include "esp_bt.h"
+#endif //CONFIG_BT_ENABLED
 #include <sys/time.h>
 #include "esp32-hal.h"