DT: nvmem: Add NXP LPC18xx EEPROM memory binding documentation

Add the devicetree binding document for NXP LPC18xx EEPROM memory.
Signed-off-by: Ariel D'Alessandro <ariel@vanguardiasur.com.ar>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/nvmem/lpc1857-eeprom.txt

+* NXP LPC18xx EEPROM memory NVMEM driver
+
+Required properties:
+  - compatible: Should be "nxp,lpc1857-eeprom"
+  - reg: Must contain an entry with the physical base address and length
+    for each entry in reg-names.
+  - reg-names: Must include the following entries.
+    - reg: EEPROM registers.
+    - mem: EEPROM address space.
+  - clocks: Must contain an entry for each entry in clock-names.
+  - clock-names: Must include the following entries.
+    - eeprom: EEPROM operating clock.
+  - resets: Should contain a reference to the reset controller asserting
+    the EEPROM in reset.
+  - interrupts: Should contain EEPROM interrupt.
+
+Example:
+
+  eeprom: eeprom@4000e000 {
+    compatible = "nxp,lpc1857-eeprom";
+    reg = <0x4000e000 0x1000>,
+          <0x20040000 0x4000>;
+    reg-names = "reg", "mem";
+    clocks = <&ccu1 CLK_CPU_EEPROM>;
+    clock-names = "eeprom";
+    resets = <&rgu 27>;
+    interrupts = <4>;
+  };