can: c_can: move runtime PM enable/disable to c_can_platform

Currently doing modprobe c_can_pci will make the kernel complain:

    Unbalanced pm_runtime_enable!

this is caused by pm_runtime_enable() called before pm is initialized.

This fix is similar to 227619c3, move those pm_enable/disable code
to c_can_platform.

Fixes: 4cdd34b2

 ("can: c_can: Add runtime PM support to Bosch C_CAN/D_CAN controller")
Link: http://lore.kernel.org/r/20210302025542.987600-1-ztong0001@gmail.com
Signed-off-by: Tong Zhang <ztong0001@gmail.com>
Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>