tests: cpu_efm32_features: add test application

tests/cpu_efm32_features/Makefile

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+include ../Makefile.tests_common
+
+BOARD = sltb001a
+
+BOARD_WHITELIST := ikea-tradfri \
+                   slstk3401a \
+                   slstk3402a \
+                   sltb001a \
+                   slwstk6000b \
+                   stk3600 \
+                   stk3700
+
+# see cpu/efm32/efm32-features.mk for the supported flags
+EFM32_UART_MODES = 1
+
+include $(RIOTBASE)/Makefile.include

tests/cpu_efm32_features/README.md

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+# EFM32 CPU Features
+
+## Introduction
+The EFM32 support several features that can be toggled compile-time.
+
+This test will ensure that RIOT-OS will compile whenever these features are toggled.
+
+## Expected result
+The test application compiles for EFM32-based boards.

tests/cpu_efm32_features/main.c

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+/*
+ * Copyright (C) 2018 Bas Stottelaar <basstottelaar@gmail.com>
+ *
+ * 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     tests
+ * @{
+ *
+ * @file
+ * @brief       Test application for EFM32 specific features.
+ *
+ * @author      Bas Stottelaar <basstottelaar@gmail.com>
+ *
+ * @}
+ */
+
+#include "periph/uart.h"
+
+int main(void)
+{
+    /* test if uart_config[i].mode is set to a know value */
+    for (unsigned i = 0; i < UART_NUMOF; i++) {
+        printf("UART %u mode: ", i);
+
+        switch (uart_config[i].mode) {
+            case UART_MODE_8N1:
+                puts("8N1");
+                break;
+            case UART_MODE_8E1:
+                puts("8E1");
+                break;
+            default:
+                puts("unknown");
+        }
+    }
+
+    return 0;
+}