kobject: Fix kernel-doc comment first line

kernel-doc comments have a prescribed format.  This includes parenthesis
on the function name.  To be _particularly_ correct we should also
capitalise the brief description and terminate it with a period.

In preparation for adding/updating kernel-doc function comments clean up
the ones currently present.

Signed-off-by: Tobin C. Harding <tobin@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>