docs/kernel-parameters: Update descriptions for "mitigations=" param with retbleed

stable inclusion
from stable-v5.10.135
commit aadc39fd5b6d43e6d96a368d9f651d01598a4ec7
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5ZWFM

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=aadc39fd5b6d43e6d96a368d9f651d01598a4ec7

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

commit ea304a8b upstream.

Updates descriptions for "mitigations=off" and "mitigations=auto,nosmt"
with the respective retbleed= settings.
Signed-off-by: NEiichi Tsukata <eiichi.tsukata@nutanix.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Cc: corbet@lwn.net
Link: https://lore.kernel.org/r/20220728043907.165688-1-eiichi.tsukata@nutanix.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -2979,6 +2979,7 @@
 					       no_entry_flush [PPC]
 					       no_uaccess_flush [PPC]
 					       mmio_stale_data=off [X86]
+					       retbleed=off [X86]
 
 				Exceptions:
 					       This does not have any effect on
@@ -3001,6 +3002,7 @@
 					       mds=full,nosmt [X86]
 					       tsx_async_abort=full,nosmt [X86]
 					       mmio_stale_data=full,nosmt [X86]
+					       retbleed=auto,nosmt [X86]
 
 	mminit_loglevel=
 			[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this