ARM: dts: AM33XX: Set pinmux for clkout2 pad used for clock output

xdma_event_intr1.clkout2 pad can be used to source clock
from either 32K OSC or any of the PLL (except MPU) outputs.
On the existing AM335x based boards (EVM, EVM-SK and Bone),
this pad is used to feed the clock to audio codes.

So, this patch configures the pinmux to get clkout2 on the pad.

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>