arm64/hugetlb: Fix building errors in huge_ptep_clear_flush()

Fix the arm64 build error which was caused by commit ae07562 ("mm:
change huge_ptep_clear_flush() to return the original pte") interacting
with commit fb396bb ("arm64/hugetlb: Drop TLB flush from
get_clear_flush()"):

  arch/arm64/mm/hugetlbpage.c: In function ‘huge_ptep_clear_flush’:
  arch/arm64/mm/hugetlbpage.c:515:9: error: implicit declaration of function ‘get_clear_flush’; did you mean ‘ptep_clear_flush’? [-Werror=implicit-function-declaration]
    515 |  return get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
        |         ^~~~~~~~~~~~~~~
        |         ptep_clear_flush

Due to the new get_clear_contig() has dropped TLB flush, we should add
an explicit TLB flush in huge_ptep_clear_flush() to keep original
semantics when changing to use new get_clear_contig().

Fixes: fb396bb ("arm64/hugetlb: Drop TLB flush from get_clear_flush()").
Fixes: ae07562 ("mm: change huge_ptep_clear_flush() to return the original pte")
Reported-and-tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Baolin Wang

arch/arm64/mm/hugetlbpage.c

@@ -507,12 +507,15 @@ pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
 {
 	size_t pgsize;
 	int ncontig;
+	pte_t orig_pte;
 
 	if (!pte_cont(READ_ONCE(*ptep)))
 		return ptep_clear_flush(vma, addr, ptep);
 
 	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
-	return get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
+	orig_pte = get_clear_contig(vma->vm_mm, addr, ptep, pgsize, ncontig);
+	flush_tlb_range(vma, addr, addr + pgsize * ncontig);
+	return orig_pte;
 }
 
 static int __init hugetlbpage_init(void)