hugetlbfs: fix some comment typos

Fix typos reserv to reserve, minimim to minimum. No functional change
intended.

Link: https://lkml.kernel.org/r/20210130092351.28072-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>