mx31/mx35/mx51/mx53/mx6: add watchdog

Use a common watchdog driver for all these cpus.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Acked-by: Stefano Babic <sbabic@denx.de>
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index bc09123..b1f4e0f 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -27,6 +27,9 @@
 
 COBJS-$(CONFIG_AT91SAM9_WATCHDOG) += at91sam9_wdt.o
 COBJS-$(CONFIG_FTWDT010_WATCHDOG) += ftwdt010_wdt.o
+ifneq (,$(filter $(SOC), mx31 mx35 mx5 mx6))
+COBJS-y += imx_watchdog.o
+endif
 COBJS-$(CONFIG_TNETV107X_WATCHDOG) += tnetv107x_wdt.o
 COBJS-$(CONFIG_S5P)               += s5p_wdt.o