omap2/3: Update omap3_defconfig to build in all the 2420 based boards

Note that booting 2420 depends on another patch posted earlier to not
select CONFIG_CPU_32v6K if CONFIG_ARCH_OMAP2 is selected.

Also note that we cannot add omap2430 in yet because of the different
clock addresses compared to 2420. Also note that we cannot have
CONFIG_CPU_32v6K=y in order to boot on 24xx.
Signed-off-by: Tony Lindgren <tony@atomide.com>