bpo-37085: Expose SocketCAN bcm_msg_head flags (GH-13646)

bpo-37085: Expose SocketCAN bcm_msg_head flags (GH-13646)

Expose the CAN_BCM SocketCAN constants used in the bcm_msg_head struct
flags (provided by <linux/can/bcm.h>) under the socket library.

This adds the following constants with a CAN_BCM prefix:

  * SETTIMER
  * STARTTIMER
  * TX_COUNTEVT
  * TX_ANNOUNCE
  * TX_CP_CAN_ID
  * RX_FILTER_ID
  * RX_CHECK_DLC
  * RX_NO_AUTOTIMER
  * RX_ANNOUNCE_RESUME
  * TX_RESET_MULTI_IDX
  * RX_RTR_FRAME
  * CAN_FD_FRAME

The CAN_FD_FRAME flag was introduced in the 4.8 kernel, while the other
ones were present since SocketCAN drivers were mainlined in 2.6.25. As
such, it is probably unnecessary to guard against these constants being
missing.
(cherry picked from commit 31c4fd2a10d90beaa37d630e5f74a471e14e089d)

Co-authored-by: karl ding <karlding@users.noreply.github.com>