fixup! tests/pkg/fatfs_vfs: use default MTD if enabled by the board

Author: gschorcht

tests/pkg/fatfs_vfs/Makefile.board.dep

@@ -0,0 +1,13 @@
+# The dependency resolution is called multiple times, but not all the
+# dependencies are resolved in the first round, such as the board deps.
+# To make sure that the board deps are resolved before running, we
+# create a temporary variable that stores the rounds and adds a `+` to
+# the string (make does not support integer incrementation).
+TEST_FATFS_DEP_ROUND := $(TEST_FATFS_DEP_ROUND)+
+
+ifeq (++,$(TEST_FATFS_DEP_ROUND))
+  ifeq (,$(filter mtd_sdcard mtd_sdmmc,$(USEMODULE)))
+    # if no SD interface is specified, use mtd_sdcard by default
+    USEMODULE += mtd_sdcard
+  endif
+endif