can: xilinx CAN controller support

This patch adds xilinx CAN controller support. This driver supports both ZYNQ
CANPS and Soft IP AXI CAN controller.

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>