arm64: cpufeature: Don't dump useless backtrace on CPU_OUT_OF_SPEC

Unfortunately, it turns out that mismatched CPU features in big.LITTLE
systems are starting to appear in the wild. Whilst we should continue to
taint the kernel with CPU_OUT_OF_SPEC for features that differ in ways
that we can't fix up, dumping a useless backtrace out of the cpufeature
code is pointless and irritating.

This patch removes the backtrace from the taint.
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

arch/arm64/kernel/cpufeature.c

@@ -639,8 +639,8 @@ void update_cpu_features(int cpu,
 	 * Mismatched CPU features are a recipe for disaster. Don't even
 	 * pretend to support them.
 	 */
-	WARN_TAINT_ONCE(taint, TAINT_CPU_OUT_OF_SPEC,
-			"Unsupported CPU feature variation.\n");
+	pr_warn_once("Unsupported CPU feature variation detected.\n");
+	add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
 }
 
 u64 read_sanitised_ftr_reg(u32 id)