x86/srso: Print mitigation for retbleed IBPB case

[ Upstream commit de9f5f7b06a5b7adbfdd8016f011120a4e928add ]

When overriding the requested mitigation with IBPB due to retbleed=ibpb,
print the mitigation in the usual format instead of a custom error
message.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/ec3af919e267773d896c240faf30bfc6a1fd6304.1693889988.git.jpoimboe@kernel.org


Stable-dep-of: dc6306ad5b0d ("x86/srso: Fix vulnerability reporting for missing microcode")
Signed-off-by: Sasha Levin <sashal@kernel.org>