[WATCHDOG] use resource_size()

Use resource_size().

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Kevin Hilman <khilman@ti.deeprootsystems.com>
Cc: Ulrik Bech Hald <ubh@ti.com>
Cc: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: Vincent Sanders <support@simtec.co.uk>
Acked-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/watchdog/at32ap700x_wdt.c b/drivers/watchdog/at32ap700x_wdt.c
index e8ae638..0378479 100644
--- a/drivers/watchdog/at32ap700x_wdt.c
+++ b/drivers/watchdog/at32ap700x_wdt.c
@@ -326,7 +326,7 @@
 		return -ENOMEM;
 	}
 
-	wdt->regs = ioremap(regs->start, regs->end - regs->start + 1);
+	wdt->regs = ioremap(regs->start, resource_size(regs));
 	if (!wdt->regs) {
 		ret = -ENOMEM;
 		dev_dbg(&pdev->dev, "could not map I/O memory\n");