mm/damon/core: disallow non-power of two min_region_sz on damon_start()

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/core: disallow non-power of two min_region_sz on damon_start()

Commit d8f867fa0825 ("mm/damon: add damon_ctx->min_sz_region") introduced

a bug that allows unaligned DAMON region address ranges. Commit

c80f46ac228b ("mm/damon/core: disallow non-power of two min_region_sz")

fixed it, but only for damon_commit_ctx() use case. Still, DAMON sysfs

interface can emit non-power of two min_region_sz via damon_start(). Fix

the path by adding the is_power_of_2() check on damon_start().

The issue was discovered by sashiko [1].