watchdog: qcom: add support for KPSS WDT

Add a driver for the watchdog timer block found in the Krait Processor
Subsystem (KPSS) on the MSM8960, APQ8064, and IPQ8064.

Signed-off-by: Josh Cartwright <joshc@codeaurora.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>