watchdog: sunxi: Fix compilation with C=2

When compiling sunxi_defconfig while using C=2, the following error
causes the compilation to fail:

    drivers/watchdog/sunxi_wdt.c:60:15: error: constant 0b0001 is not a valid number

Fix it by using hex notation instead of the non-standard binary one

Signed-off-by: Emilio Lopez <emilio@elopez.com.ar>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>