watchdog: i.MX: use IMX_HAVE_PLATFORM_IMX2_WDT to depend on

The i.MX architecture provides IMX_HAVE_PLATFORM_* macros to signal
that a selected SoC supports a certain hardware. Use them instead of
depending on ARCH_* directly.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Cc: linux-watchdog@vger.kernel.org

drivers/watchdog/Kconfig

@@ -330,7 +330,7 @@ config MAX63XX_WATCHDOG
 
 config IMX2_WDT
 	tristate "IMX2+ Watchdog"
-	depends on ARCH_MX2 || ARCH_MX25 || ARCH_MX3 || ARCH_MX5
+	depends on IMX_HAVE_PLATFORM_IMX2_WDT
 	help
 	  This is the driver for the hardware watchdog
 	  on the Freescale IMX2 and later processors.