[N9H30] Fix SDH driver building.

bsp/nuvoton/libraries/n9h30/Driver/Include/nu_sdh.h

@@ -645,7 +645,6 @@ typedef struct SDH_info_t
 /*@}*/ /* end of group N9H30_SDH_EXPORTED_TYPEDEF */
 
 /// @cond HIDDEN_SYMBOLS
-extern SDH_INFO_T SD0, SD1;
 
 /// @endcond HIDDEN_SYMBOLS