doc-dyndbg: describe "class CLASS_NAME" query support

Add an explanation of the new "class CLASS_NAME" syntax and meaning,
noting that the module determines if CLASS_NAME applies to it.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-19-jim.cromie@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>