mm: don't play games with pinned pages in clear_page_refs

stable inclusion
from stable-5.10.9
commit 1eea108995a2411d46350bf43e4b316a9f1e30fd
bugzilla: 47457

--------------------------------

[ Upstream commit 9348b73c ]

Turning a pinned page read-only breaks the pinning after COW.  Don't do it.

The whole "track page soft dirty" state doesn't work with pinned pages
anyway, since the page might be dirtied by the pinning entity without
ever being noticed in the page tables.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>