ARM: OMAP: Add maintainer entry for IGEP machines

Enric and I have been mantained this machine and while we
are moving to device trees, it is good that people cc us
when reporting bugs or regression on the board file until
we have proper DT support.

Signed-off-by: Javier Martinez Canillas <javier@dowhile0.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>