Conditionally compile code for specific roles.

This allows NimBLE options in menuconfig to reduce code size based on
the roles selected (scan/advertising/central/peripheral).

Significant code space can be saved by removing unnecessary roles for the application.

src/NimBLERemoteDescriptor.h

@@ -3,7 +3,7 @@
  *
  *  Created: on Jan 27 2020
  *      Author H2zero
- * 
+ *
  * Originally:
  *
  * BLERemoteDescriptor.h
@@ -17,6 +17,9 @@
 #include "sdkconfig.h"
 #if defined(CONFIG_BT_ENABLED)
 
+#include "nimconfig.h"
+#if defined( CONFIG_BT_NIMBLE_ROLE_CENTRAL)
+
 #include "NimBLERemoteCharacteristic.h"
 
 class NimBLERemoteCharacteristic;
@@ -54,5 +57,7 @@ private:
 
 
 };
+
+#endif // #if defined( CONFIG_BT_NIMBLE_ROLE_CENTRAL)
 #endif /* CONFIG_BT_ENABLED */
 #endif /* COMPONENTS_NIMBLEREMOTEDESCRIPTOR_H_ */