x86/srso: Add IBPB on VMEXIT

stable inclusion
from stable-v5.10.189
commit 384d41bea948a18288aff668b7bdf3b522b7bf73
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I7RQ67
CVE: CVE-2023-20569

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=384d41bea948a18288aff668b7bdf3b522b7bf73



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

Upstream commit: d893832d

Add the option to flush IBPB only on VMEXIT in order to protect from
malicious guests but one otherwise trusts the software that runs on the
hypervisor.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>