dt-bindings: i2c: i2c-imx-lpi2c: add ipg clk

i.MX LPI2C actually requires dual clock: per clock and ipg clock, so add
both.
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Documentation/devicetree/bindings/i2c/i2c-imx-lpi2c.yaml

@@ -37,10 +37,12 @@ properties:
   clock-frequency: true
 
   clock-names:
-    maxItems: 1
+    items:
+      - const: per
+      - const: ipg
 
   clocks:
-    maxItems: 1
+    maxItems: 2
 
   power-domains:
     maxItems: 1
@@ -63,5 +65,6 @@ examples:
         reg = <0x40A50000 0x10000>;
         interrupt-parent = <&intc>;
         interrupts = <GIC_SPI 37 IRQ_TYPE_LEVEL_HIGH>;
-        clocks = <&clks IMX7ULP_CLK_LPI2C7>;
+        clocks = <&clks IMX7ULP_CLK_LPI2C7>,
+                 <&clks IMX7ULP_CLK_NIC1_BUS_DIV>;
     };