sp5100_tco: Add AMD Carrizo platform support

sp5100_tco watchdog is also supported on AMD KernCZ chipset of Carrizo
platform.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Cc: Denis Turischev <denis.turischev@compulab.co.il>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>