fix omap2 kconfig goofage

Clean up OMAP2 Kconfig.  Again.

 - 34xx shouldn't go in the middle of the 24xx stuff, it
   goofs the dependency tree displayed by e.g. kconfig.
   In particular, not in the middle of the H4-specific
   options.

 - Make the 2420 boards depend on OMAP2420, and 2430 boards
   on OMAP2430 ... a 2420-only kernel shouldn't show 2430
   boards, and vice versa.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>