can: flexcan: adding platform specific details for LS1021A

This patch adds platform specific details for NXP SOC LS1021A to the
flexcan driver code.

Signed-off-by: Pankaj Bansal <pankaj.bansal@nxp.com>
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@freescale.com>
Reviewed-by: Zhengxiong Jin <Jason.Jin@freescale.com>
Reviewed-by: Poonam Aggrwal <poonam.aggrwal@nxp.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>