cpu: added place for shared STM32 files

cpu/stm32_common/Makefile

+DIRS = periph
+
+include $(RIOTBASE)/Makefile.base

cpu/stm32_common/Makefile.include

+# export the CPU family so we can differentiate between them in the code
+FAM = $(shell echo $(CPU_FAM) | tr 'a-z-' 'A-Z_')
+export CFLAGS += -DCPU_FAM_$(FAM)
+
+# includ common periph module
+USEMODULE += periph_common
+
+# export the common include directory
+export INCLUDES += -I$(RIOTCPU)/stm32_common/include

cpu/stm32_common/include/periph_cpu_common.h

+/*
+ * Copyright (C) 2016 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup         cpu_stm32_common
+ * @{
+ *
+ * @file
+ * @brief           Shared CPU specific definitions for the STM32 family
+ *
+ * @author          Hauke Petersen <hauke.peterse@fu-berlin.de>
+ */
+
+#ifndef PERIPH_CPU_COMMON_H
+#define PERIPH_CPU_COMMON_H
+
+#include "cpu.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Use the shared SPI functions
+ * @{
+ */
+#define PERIPH_SPI_NEEDS_TRANSFER_BYTES
+#define PERIPH_SPI_NEEDS_TRANSFER_REG
+#define PERIPH_SPI_NEEDS_TRANSFER_REGS
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PERIPH_CPU_COMMON_H */
+/** @} */

cpu/stm32_common/periph/Makefile

+MODULE = periph
+
+include $(RIOTBASE)/Makefile.base