docbook: add idr/ida to kernel-api docbook

Add idr/ida to kernel-api docbook.
Fix typos and kernel-doc notation.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Naohiro Aota <naota@elisp.net>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>