mm/damon: rename min_sz_region of damon_ctx to min_region_sz

mm/damon: rename min_sz_region of damon_ctx to min_region_sz

'min_sz_region' field of 'struct damon_ctx' represents the minimum size of
each DAMON region for the context.  'struct damos_access_pattern' has a
field of the same name.  It confuses readers and makes 'grep' less optimal
for them.  Rename it to 'min_region_sz'.

Link: https://lkml.kernel.org/r/20260117175256.82826-9-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>