ARM: dts: Enable emmc on hp t410

There's a 2GB emmc on hp t410 that's wired to the sd_2 interface.
Note that we also need to configure the evtmux using edma_xbar for
edma channels.

Let's use the McASP2 channels like the original kernel seems to be
doing, most likely the audio on t410 is different from dm814x-evm.

Reviewed-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>