mm: hugetlb_vmemmap: replace early_param() with core_param()

After the following commit:

  78f39084

 ("mm: hugetlb_vmemmap: add hugetlb_optimize_vmemmap sysctl")

There is no order requirement between the parameter of
"hugetlb_free_vmemmap" and "hugepages" since we have removed the check of
whether HVO is enabled from hugetlb_vmemmap_init().  Therefore we can
safely replace early_param() with core_param() to simplify the code.

Link: https://lkml.kernel.org/r/20220628092235.91270-6-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Will Deacon <will@kernel.org>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>