clock_control: Introduce mcux ccm driver

Adds a new clock control driver for i.MX SoCs that have the clock
control module (CCM).

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>

dts/bindings/clock/nxp,imx-ccm.yaml

@@ -0,0 +1,39 @@
+#
+# Copyright (c) 2017, NXP
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+---
+title: i.MX Clock Controller Module (CCM)
+id: nxp,imx-ccm
+version: 0.1
+
+description: >
+    This is a representation of the i.MX CCM IP node
+
+properties:
+  - compatible:
+      type: string
+      category: required
+      description: compatible strings
+      constraint: "nxp,imx-ccm"
+
+  - reg:
+      type: int
+      description: mmio register space
+      generation: define
+      category: required
+
+  - label:
+      type: string
+      category: required
+      description: Human readable string describing the device (used by Zephyr for API name)
+      generation: define
+
+cell_string: CCM_CLK
+
+"#cells":
+  - name
+  - offset
+  - bits
+...