serial: stm32: remove unnecessary trace

Remove the trace indicating the end of the DEBUG initialization

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/drivers/serial/serial_stm32.c b/drivers/serial/serial_stm32.c
index e31c87b..315b5a2 100644
--- a/drivers/serial/serial_stm32.c
+++ b/drivers/serial/serial_stm32.c
@@ -269,7 +269,6 @@
 	_stm32_serial_setbrg(base, uart_info,
 			     CONFIG_DEBUG_UART_CLOCK,
 			     CONFIG_BAUDRATE);
-	printf("DEBUG done\n");
 }
 
 static inline void _debug_uart_putc(int c)