x86/spectre: Add missing family 6 check to microcode check

The check for Spectre microcodes does not check for family 6, only the
model numbers.

Add a family 6 check to avoid ambiguity with other families.

Fixes: a5b296636453 ("x86/cpufeature: Blacklist SPEC_CTRL/PRED_CMD on early Spectre v2 microcodes")
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180824170351.34874-2-andi@firstfloor.org

arch/x86/kernel/cpu/intel.c

@@ -150,6 +150,9 @@ static bool bad_spectre_microcode(struct cpuinfo_x86 *c)
 	if (cpu_has(c, X86_FEATURE_HYPERVISOR))
 		return false;
 
+	if (c->x86 != 6)
+		return false;
+
 	for (i = 0; i < ARRAY_SIZE(spectre_bad_microcodes); i++) {
 		if (c->x86_model == spectre_bad_microcodes[i].model &&
 		    c->x86_stepping == spectre_bad_microcodes[i].stepping)