ANDROID: db845c: add 2 more symbols to the list

In commit 3e72558c ("can: mcp251xfd: fix infinite loop when xmit
fails"), the mcp251xfd driver fixes a bug, and calls 2 new functions,
can_free_echo_skb and work_busy.  Add them to the db845c symbol list so
that the build continues to work properly.

Fixes: 3e72558c ("can: mcp251xfd: fix infinite loop when xmit fails")
Change-Id: Icd7221db8b185bad58355c0f6b3e498342983d1d
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>