can: rcar: Kconfig: Add helper dependency on COMPILE_TEST

it's helpful for complie test in other platform(e.g.X86)

Link: https://lore.kernel.org/r/20210825062341.2332-1-caihuoqing@baidu.com
Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>