nouveau: fix migrate_to_ram() for faulting page

mainline inclusion
from mainline-v6.1-rc2
commit 97061d44
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5VZ0L

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=97061d441110528dc02972818f2f1dad485107f9

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Commit 16ce101d ("mm/memory.c: fix race when faulting a device private
page") changed the migrate_to_ram() callback to take a reference on the
device page to ensure it can't be freed while handling the fault.
Unfortunately the corresponding update to Nouveau to accommodate this
change was inadvertently dropped from that patch causing GPU to CPU
migration to fail so add it here.

Link: https://lkml.kernel.org/r/20221019122934.866205-1-apopple@nvidia.com


Fixes: 16ce101d ("mm/memory.c: fix race when faulting a device private page")
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Reviewed-by: tong tiangen <tongtiangen@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>