[CPUFREQ] Limit return value of speedstep_get_state()

Looking around speedstep-smi, there is a lot of call to
speedstep_get_state() which is used as an index for the array
speedstep_freqs.  But speedstep_get_state() will return the value of ebx
after a call to a SMI handler.  It's not safe IMHO.

From: Bruno Ducrot
Signed-off-by: Dave Jones <davej@redhat.com>

arch/i386/kernel/cpu/cpufreq/speedstep-smi.c

@@ -139,7 +139,7 @@ static int speedstep_get_state (void)
 		: "a" (command), "b" (function), "c" (0), "d" (smi_port), "S" (0)
 	);
 
-	return state;
+	return (state & 1);
 }
 
 /**