mm: remove arch_flush_tlb_batched_pending() arch helper

mm: remove arch_flush_tlb_batched_pending() arch helper

Since commit 4b634918384c ("arm64/mm: Close theoretical race where stale
TLB entry remains valid"), all arches that use tlbbatch for reclaim
(arm64, riscv, x86) implement arch_flush_tlb_batched_pending() with a
flush_tlb_mm().

So let's simplify by removing the unnecessary abstraction and doing the
flush_tlb_mm() directly in flush_tlb_batched_pending().  This effectively
reverts commit db6c1f6f236d ("mm/tlbbatch: introduce
arch_flush_tlb_batched_pending()").

Link: https://lkml.kernel.org/r/20250609103132.447370-1-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Suggested-by: Will Deacon <will@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>