arm/dts: twl6030: Add DTS file for twl6030 PMIC

Add a dedicated DTS file for the twl6030 Power IC.
This chip is a big SoC that will be reused in a lot of various
OMAP4+ boards.

Note: This file is supposed to be included in a board DTS that will
create the twl node in order to allow the &twl reference to work.

Exmaple:
...
&i2c1 {
    twl: twl@48 {
        reg = <0x48>;
        interrupts = <0 7 4>;
        interrupt-controller;
        interrupt-parent = <&gic>;
    };
};

/include/ "twl6030.dtsi"
...

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Rob Herring <rob.herring@calxeda.com>