cpu/sam0_common: add script to generate Kconfig files for all parts

e.g. Usage:

	./sam0_common/dist/kconfig_gen.sh samd51

cpu/sam0_common/dist/kconfig_gen.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+#
+# Generate Kconfig file for all parts of a sam0 family
+# based on the available vendor files.
+
+if [ -z "$1" ]
+then
+    echo "usage: $0 <family>"
+    exit 1
+fi
+
+FAM=$1
+FAM_UC=$(echo $FAM | tr a-z A-Z)
+
+VENDOR_FILES=$(dirname $0)/../include/vendor/$FAM/*/$FAM?*.h
+
+{
+echo '## CPU Models'
+for i in $VENDOR_FILES; do
+    MODEL_LC=$(basename $i .h)
+    MODEL_UC=$(echo $MODEL_LC | tr a-z A-Z)
+
+    echo "config CPU_MODEL_$MODEL_UC"
+    echo "    bool"
+    echo "    select CPU_FAM_$FAM_UC"
+    echo ""
+done
+
+echo 'config CPU_MODEL'
+for i in $VENDOR_FILES; do
+    MODEL_LC=$(basename $i .h)
+    MODEL_UC=$(echo $MODEL_LC | tr a-z A-Z)
+    printf '    default "%s" if CPU_MODEL_%s\n' $MODEL_LC $MODEL_UC
+done
+} > Kconfig.$FAM