omap: Fix omap_4430sdp_defconfig for make oldconfig

Commit ffb63e34 changed
Kconfig to select support for omap2, 3 and 4 by default.

However, CONFIG_SMP won't currently work properly on
uniprocessor ARMs, or if support for earlier ARM cores
is selected in.

Fix this by updating omap_4430sdp_defconfig to not
select omap2 or 3 at this point.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>