Move usart files to common area

Again added to L1 which is similar to F1

lib/stm32/f2/Makefile

@@ -30,7 +30,8 @@ CFLAGS		= -Os -g -Wall -Wextra -I../../../include -fno-common \
 ARFLAGS		= rcs
 OBJS		= rcc.o gpio.o usart.o flash.o \
 		  i2c.o exti2.o timer.o \
-		  gpio_common_all.o gpio_common_f24.o spi_common_all.o dac_common_all.o
+		  gpio_common_all.o gpio_common_f24.o spi_common_all.o dac_common_all.o \
+              usart_common_all.o
 
 VPATH += ../../usb:../:../../cm3:../common
 

lib/stm32/f2/usart.c

@@ -0,0 +1,28 @@
+/** @defgroup usart_file USART
+
+@ingroup STM32F2xx
+
+@brief <b>libopencm3 STM32F2xx USART</b>
+
+*/
+
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libopencm3/stm32/usart.h>
+#include <libopencm3/stm32/common/usart_common_all.h>
+