Fix wrong define

thanks to sm32duino forum user who report this here:
http://stm32duino.com/viewtopic.php?f=29&t=4159

Signed-off-by: Frederic.Pillon <[email protected]>

Author: fpistm

cores/arduino/HardwareSerial.cpp

@@ -33,7 +33,7 @@
 #if defined(HAL_UART_MODULE_ENABLED)
 #if defined(HAVE_HWSERIAL1) || defined(HAVE_HWSERIAL2) || defined(HAVE_HWSERIAL3) ||\
     defined(HAVE_HWSERIAL4) || defined(HAVE_HWSERIAL5) || defined(HAVE_HWSERIAL6) ||\
-    defined(HAVE_HWSERIAL7) || defined(HAVE_HWSERIAL8) || defined(HAVE_HWSERIAL8) ||\
+    defined(HAVE_HWSERIAL7) || defined(HAVE_HWSERIAL8) || defined(HAVE_HWSERIAL9) ||\
     defined(HAVE_HWSERIAL10) || defined(HAVE_HWSERIALLP1)
 // SerialEvent functions are weak, so when the user doesn't define them,
 // the linker just sets their address to 0 (which is checked below).