The driver was updated for OMAP34xx, but the Kconfig file was missed.
So this adds the missing parts from d99241c in Tony Lindgren's tree:

    Add watchdog timer support for TI OMAP3430.
Signed-off-by: Madhusudhan Chikkature <madhu.cr@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>