UPSTREAM: arm64: tlb: remove redundant barrier from __flush_tlb_pgtable

__flush_tlb_pgtable is used to invalidate intermediate page table
entries after they have been cleared and are about to be freed. Since
pXd_clear imply memory barriers, we don't need the extra one here.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Bug: 31432001
Change-Id: Ibcad1a823f8af667504f7f8060b33841666d015d
(cherry picked from commit 28c6fbc3b446caf5f8d1f2d7b79e09e743158a4d)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>