ARM: davinci_all_defconfig: set CONFIG_DAVINCI_WATCHDOG=y

This changes CONFIG_DAVINCI_WATCHDOG from a module to a compiled-in
option. Since the reset function has been moved out of the mach code in
commit 94f2e945 ("ARM: davinci: remove watchdog reset") and into the
watchdog driver, devices cannot reboot unless the watchdog driver is
loaded, so make it a compiled-in option so that we can always reboot, even
when modules are not loaded.

Cc: Sekhar Nori <nsekhar@ti.com>
Suggested-by: Adam Ford <aford173@gmail.com>
Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>