risc-v/rv32m1: Fix wrong position for ++ operator on serial driver

Signed-off-by: Gustavo Henrique Nihei <gustavo.nihei@espressif.com>

arch/risc-v/src/rv32m1/rv32m1_serial.c

@@ -491,7 +491,7 @@ static void up_set_format(struct uart_dev_s *dev)
           /* Get the closer one. i.e. the minimum difference */
 
           tdiff = priv->baud - baud;
-          tsbr ++;
+          tsbr++;
         }
 
       /* Pick up the best osr and sbr with the minimum diff */