gpio/twl: Add DT support to gpio-twl4030 driver

Add the DT support for the I2C GPIO expander inside the twl4030.

Note: The pdata parameters still have to be properly adapted using
dedicated bindings.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>