arm64: hugetlb: Restore TLB invalidation for BBM on contiguous ptes

Commit fb396bb459c1 ("arm64/hugetlb: Drop TLB flush from get_clear_flush()")
removed TLB invalidation from get_clear_flush() [now get_clear_contig()]
on the basis that the core TLB invalidation code is aware of hugetlb
mappings backed by contiguous page-table entries and will cover the
correct virtual address range.

However, this change also resulted in the TLB invalidation being removed
from the "break" step in the break-before-make (BBM) sequence used
internally by huge_ptep_set_{access_flags,wrprotect}(), therefore
making the BBM sequence unsafe irrespective of later invalidation.

Although the architecture is desperately unclear about how exactly
contiguous ptes should be updated in a live page-table, restore TLB
invalidation to our BBM sequence under the assumption that BBM is the
right thing to be doing in the first place.

Fixes: fb396bb459c1 ("arm64/hugetlb: Drop TLB flush from get_clear_flush()")
Cc: Ard Biesheuvel <[email protected]>
Cc: Steve Capper <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Marc Zyngier <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Reviewed-by: Anshuman Khandual <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Catalin Marinas <[email protected]>

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