Changing pfn on a user page table mapped entry, without first going through
break-before-make (BBM) procedure is unsafe. This just updates set_pte_at()
to intercept such changes, via an updated pgattr_change_is_safe(). This new
check happens via __check_racy_pte_update(), which has now been renamed as
__check_safe_pte_update().

Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20230130121457.1607675-1-anshuman.khandual@arm.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>