ARM: dts: Fix swapped mmc order for omap3

Also some omap3 devices like n900 seem to have eMMC and micro-sd swapped
around with commit 21b2cec6

 ("mmc: Set PROBE_PREFER_ASYNCHRONOUS for
drivers that existed in v4.4").

Let's fix the issue with aliases as discussed on the mailing lists. While
the mmc aliases should be board specific, let's first fix the issue with
minimal changes.

Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>