Documentation: checkpatch: Add TRAILING_SEMICOLON message

Add a new message type TRAILING_SEMICOLON for the macro definitions
that conclude with a semicolon.

Suggested-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Utkarsh Verma <utkarshverma294@gmail.com>
Link: https://lore.kernel.org/r/20210904074201.13532-1-utkarshverma294@gmail.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>