x86/bugs: Qualify RETBLEED_INTEL_MSG

When retbleed mitigation is disabled, the kernel already prints an info
message that the system is vulnerable.  Recent code restructuring also
inadvertently led to RETBLEED_INTEL_MSG being printed as an error, which is
unnecessary as retbleed mitigation was already explicitly disabled (by config
option, cmdline, etc.).

Qualify this print statement so the warning is not printed unless an actual
retbleed mitigation was selected and is being disabled due to incompatibility
with spectre_v2.

Fixes: e3b78a7a ("x86/bugs: Restructure retbleed mitigation")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220624


Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20251003171936.155391-1-david.kaplan@amd.com