MAINTAINERS: update HUGETLB reviewers

I have done quite some review on hugetlb code over the years, and some
work on it as well, the latest being the hugetlb pagewalk unification
which is a work in progress, and touches hugetlb code to great lengths.

HugeTLB does not have many reviewers, so I would like to help out by
offering myself as an official Reviewer.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
Link: https://lkml.kernel.org/r/20250409082452.269180-1-osalvador@suse.de
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Muchun Song <muchun.song@linux.dev>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

MAINTAINERS

@@ -10954,6 +10954,7 @@ F:	include/linux/platform_data/huawei-gaokun-ec.h
 
 HUGETLB SUBSYSTEM
 M:	Muchun Song <muchun.song@linux.dev>
+R:	Oscar Salvador <osalvador@suse.de>
 L:	linux-mm@kvack.org
 S:	Maintained
 F:	Documentation/ABI/testing/sysfs-kernel-mm-hugepages