OMAP3: igep00x0: Reduce lines of code for IGEP-based boards.

This is rework on config files of IGEP-based boards with the aim to remove
duplicated code to be more maintainable. Basically this patch creates a
common configuration file for both boards and only sets the specific option
in the board config file.

On board files the hardcored mach type was replaced in favour of using the
CONFIG_MACH_TYPE option.

More than 200 duplicated lines have been deleted.

Signed-off-by: Enric Balletbo i Serra <eballetbo@gmail.com>