Add support for CONFIG_PM which is the new way to handle managing clocks.

Move the clock management to pm_runtime_resume() and pm_runtime_suspend()
callbacks for the driver.

CONFIG_PM is required by OMAP based devices to handle clock management.
Therefore, this allows future Texas Instruments SoCs that have the MCAN IP
to work with this driver.
Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>