igep0020: Enable DISTRO_DEFAULTS on IGEPv2 platforms

Like commit 3337e3af this enables suitable commands needed for booting
general purpose Linux distribution. This is required for example if we want
to use PXE or DHCP as default boot targets, symbols no longer enabled by
config_distro_defaults.h.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>