ARM: SAMSUNG: Reduce virtual memory size for WDT device

This patch reduces the virtual memory allocated for WDT device from 1M
to 1K.

Signed-off-by: Banajit Goswami <banajit.g@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Acked-by: Ben Dooks <ben-linux@fluff.org>