docs: dev-tools: coccinelle: Update documentation

* Fix install instruction by adding `./autogen` command
  before `./configure`.
* Add link to a more detailed installation instruction.
* Add link to SmPL grammar documentation.
* Add single space after ',' to slightly improve readability.

Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>