Refine the preprocessor conditional guard style (#190)

graphics/nxbe/nxbe_flush.c

@@ -108,4 +108,4 @@ void nxbe_flush(FAR struct nxbe_window_s *wnd,
     }
 }
 
-#endif  /* CONFIG_NX_RAMBACKED */
+#endif /* CONFIG_NX_RAMBACKED */

graphics/nxmu/nxmu.h

@@ -291,4 +291,4 @@ void nxmu_kbdin(FAR struct nxmu_state_s *nxmu, uint8_t nch, FAR uint8_t *ch);
 }
 #endif
 
-#endif  /* __GRAPHICS_NXMU_NXMU_H */
+#endif /* __GRAPHICS_NXMU_NXMU_H */