i2c: cros-ec-tunnel: Mark ACPI and OF related data as maybe unused

The driver can be compile tested with !CONFIG_OF or !CONFIG_ACPI making
certain data unused:

  drivers/i2c/busses/i2c-cros-ec-tunnel.c:295:34: error: ‘cros_ec_i2c_of_match’ defined but not used [-Werror=unused-const-variable=]

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>