platform/chrome: cros_usbpd_notify: Add driver data struct

Introduce a device driver data structure, cros_usbpd_notify_data, in
which we can store the notifier block object and pointers to the struct
cros_ec_device and struct device objects.

This will make it more convenient to access these pointers when
executing both platform and ACPI callbacks.

Signed-off-by: Prashant Malani <pmalani@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Benson Leung <bleung@chromium.org>