arm: exx32: Add Silabs EFM32WG soc files

The Silicon Labs EFM32 Wonder Gecko MCU includes:

        * Cortex-M4F core at 48MHz
        * up to 256KB of flash and 32KB of RAM
        * USB with host and OTG support
        * multiple low power peripherals

Signed-off-by: Christian Taedcke <hacking@taedcke.com>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>

arch/arm/soc/silabs_exx32/efm32wg/soc.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2017 Christian Taedcke
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file
+ * @brief Board configuration macros for the efm32wg soc
+ *
+ */
+
+#ifndef _SOC__H_
+#define _SOC__H_
+
+#include <misc/util.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef _ASMLANGUAGE
+
+#include <em_common.h>
+#include <device.h>
+
+#include "soc_pinmap.h"
+#include "../common/soc_gpio.h"
+
+#endif /* !_ASMLANGUAGE */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _SOC__H_ */