ARM: dts: omap4-panda: Update the LED support for the panda

The GPIO for LED D1 on the omap4-panda a1-a3 rev and the omap4-panda-es
are different.

A1-A3 = gpio_wk7
ES = gpio_110

There is no change to LED D2

Abstract away the pinmux and the LED definitions for the two boards into
the respective DTS files.

Signed-off-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>