mfd: cros_ec: Add convenience struct to define dedicated CrOS EC MCUs

mfd: cros_ec: Add convenience struct to define dedicated CrOS EC MCUs

With the increasing use of dedicated CrOS EC MCUs, it takes a fair amount
of boiler plate code to add those devices, add a struct that can be used
to specify a dedicated CrOS EC MCU so we can just add a new item to it to
define a new dedicated MCU.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>