kernel-doc: cleanup perl script

Various cleanups of scripts/kernel-doc:
- don't use **/ as an ending kernel-doc block since it's not preferred;
- typos/spellos
- add whitespace around ==, after comma, & around . operator;
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>