can: dev: add CAN interface API for fixed bitrates

Some CAN interfaces only support fixed fixed bitrates. This patch adds a
netlink interface to get the list of the CAN interface's fixed bitrates and
data bitrates.

Inside the driver arrays of supported data- bitrate values are defined.

const u32 drvname_bitrate[] = { 20000, 50000, 100000 };
const u32 drvname_data_bitrate[] = { 200000, 500000, 1000000 };

struct drvname_priv *priv;
priv = netdev_priv(dev);

priv->bitrate_const = drvname_bitrate;
priv->bitrate_const_cnt = ARRAY_SIZE(drvname_bitrate);
priv->data_bitrate_const = drvname_data_bitrate;
priv->data_bitrate_const_cnt = ARRAY_SIZE(drvname_data_bitrate);

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>