serdev: serdev.h: clean up kernel-doc comments

serdev: serdev.h: clean up kernel-doc comments

Correct kernel-doc comment format and add a missing to avoid
kernel-doc warnings:

Warning: include/linux/serdev.h:49 struct member 'write_comp' not
 described in 'serdev_device'
Warning: include/linux/serdev.h:49 struct member 'write_lock' not
 described in 'serdev_device'
Warning: include/linux/serdev.h:68 struct member 'shutdown' not described
 in 'serdev_device_driver'
Warning: include/linux/serdev.h:134 function parameter 'serdev' not
 described in 'serdev_device_put'
Warning: include/linux/serdev.h:162 function parameter 'ctrl' not
 described in 'serdev_controller_put'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20260311052347.305612-1-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>