Fix stm32update.py script

Exit if STM32 serie to add already exists

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

CI/utils/stm32update.py

@@ -562,6 +562,7 @@ def main():
             stm32_list = [upargs.add.upper()]
         else:
             print(upargs.add + " can't be added as it already exists!")
+            exit(1)
     updateSTRepo()
     if upargs.check:
         printVersion()