ARM: 9197/1: spectre-bhb: fix loop8 sequence for Thumb2

stable inclusion
from stable-4.19.245
commit 047794b3cfaff4313f379d0cb0509f1c0b972e26
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5FNPY


CVE: NA

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[ Upstream commit 3cfb3019 ]

In Thumb2, 'b . + 4' produces a branch instruction that uses a narrow
encoding, and so it does not jump to the following instruction as
expected. So use W(b) instead.

Fixes: 6c7cb60b ("ARM: fix Thumb2 regression with Spectre BHB")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>