mm: Fix TLB flush for not-first PFNMAP mappings in unmap_region()

stable inclusion
from stable-v5.10.144
commit 891f03f688de8418f44b32b88f6b4faed5b2aa81
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6D0V7

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=891f03f688de8418f44b32b88f6b4faed5b2aa81



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This is a stable-specific patch.
I botched the stable-specific rewrite of
commit b67fbebd ("mmu_gather: Force tlb-flush VM_PFNMAP vmas"):
As Hugh pointed out, unmap_region() actually operates on a list of VMAs,
and the variable "vma" merely points to the first VMA in that list.
So if we want to check whether any of the VMAs we're operating on is
PFNMAP or MIXEDMAP, we have to iterate through the list and check each VMA.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>
Reviewed-by: Zheng Zengkai <zhengzengkai@huawei.com>