mm/damon: remove some unneeded function definitions in damon.h

mm/damon: remove some unneeded function definitions in damon.h

In damon.h some func definitions about VA & PA can only be used in its
own file, so there no need to define in the header file, and the header
file will look cleaner.

If other files later need these functions, the prototypes can be added
to damon.h at that time.

[sj@kernel.org: remove unnecessary function prototype position changes]
Link: https://lkml.kernel.org/r/20211118114827.20052-1-sj@kernel.org
Link: https://lkml.kernel.org/r/45fd5b3ef6cce8e28dbc1c92f9dc845ccfc949d7.1636989871.git.xhao@linux.alibaba.com
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>