kinetis: reorganise soc directory using soc family

Add Kinetis SoC family and rename fsl_frdm_k64f to mk64f12.
This will allow adding new SoCs of the same family and the reuse of code
among SoCs of the family and series.

Change-Id: Iea1a663aef7ce0487f147bdd36f668bebe80deb5
Signed-off-by: Anas Nashif <anas.nashif@intel.com>

arch/arm/soc/nxp_kinetis/Kconfig

@@ -0,0 +1,28 @@
+#
+# Copyright (c) 2016 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+config SOC_FAMILY_KINETIS
+	bool
+	# omit prompt to signify a "hidden" option
+	default n
+
+if SOC_FAMILY_KINETIS
+config SOC_FAMILY
+	string
+	default "nxp_kinetis"
+endif
+
+source "arch/arm/soc/nxp_kinetis/*/Kconfig.soc"