[ARM] omap: watchdog: allow OMAP watchdog driver on OMAP34xx platforms

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>