mm/damon: remove unnecessary type castings

Remove unnecessary void* type castings.

Link: https://lkml.kernel.org/r/20220421153056.8474-1-yuzhe@nfschina.com


Signed-off-by: Yu Zhe <yuzhe@nfschina.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: liqiong <liqiong@nfschina.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>