UPSTREAM: mm/damon: move damon_rand() definition into damon.h

damon_rand() is called in three files:damon/core.c, damon/ paddr.c,
damon/vaddr.c, i think there is no need to redefine this twice, So move
it to damon.h will be a good choice.

Link: https://lkml.kernel.org/r/20211202075859.51341-1-xhao@linux.alibaba.com


Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

(cherry picked from commit 9b2a38d6)

Bug: 228223814
Signed-off-by: Hailong Tu <tuhailong@oppo.com>
Change-Id: Ib7be3062385fac4b422faa86705968aa39095a72