include/linux/damon.h: fix kernel-doc comments for 'damon_callback'

A few Kernel-doc comments in 'damon.h' are broken.  This fixes them.

Link: https://lkml.kernel.org/r/20210917123958.3819-5-sj@kernel.org


Signed-off-by: SeongJae Park <sjpark@amazon.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>