ARM: dts: omap5-uevm: Add uart pinctrl data

Booting omap5 uevm results in the following error
"did not get pins for uart error: -19"

This happens because omap5 uevm dts file is not adapted
to use uart through pinctrl framework.
Populate uart pinctrl data to get rid of the error.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
[r.sricharan@ti.com: Replaced constants with preprocessor macros]
Signed-off-by: Sricharan R <r.sricharan@ti.com>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>