modules: moduleparam.h: fix kernel-doc comments

modules: moduleparam.h: fix kernel-doc comments

Fix kernel-doc comments to prevent kernel-doc warnings:

Warning: include/linux/moduleparam.h:364 function parameter 'arg' not
 described in '__core_param_cb'
Warning: include/linux/moduleparam.h:395 No description found for return
 value of 'parameq'
Warning: include/linux/moduleparam.h:405 No description found for return
 value of 'parameqn'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
[Sami: Clarified the commit message]
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>