can: Merge rh850.c from 3.18

1.can: Don't sent fw_br command
Older versions of rh850 get stuck when
fw_br command received.

2.can: Fix buffer calculation

3.can: rh850 support for CAN FD
This change enables dual mode for CAN raw frames and also CAN FD for property transfer with up to
64 bytes payload for both transmit and receive.

4.can: rh850 CAN FD backward compatibility
This change enables backward compatibility for previous versions of VNW framework to use legacy raw frame mode.

5.can: rh850 support for AMB mode
This enables the AMB driver mode to support
CAN FD frames sent while driver mode is AMB

Change-Id: I0b6939f29ebabeebe2fd32a26fcc67c4386a6cb4
Signed-off-by: Bruce Wu <brucewu@codeaurora.org>