watchdog: sunxi: support parameterized compatible strings

This patch adds support for hardware parameters tied to compatible
strings, so similar hardware can reuse the driver.

This will be used to support the newer watchdog found in A31 and
later SoCs. Differences in the new hardware include separate
interrupt lines for each watchdog, and corresponding interrupt
control/status registers. Watchdog control registers were also
slightly rearranged.

Also replace ioread32()/iowrite32() with readl()/writel() in various
places changed.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>