[CPUFREQ] Fix an invalid comment in speedstep-ich

This driver is for ICH only, not for PIIX4. Thanks to Christian Hilberg for noting this.

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

@@ -179,7 +179,7 @@ static int speedstep_activate (void)
 /**
  * speedstep_detect_chipset - detect the Southbridge which contains SpeedStep logic
  *
- *   Detects PIIX4, ICH2-M and ICH3-M so far. The pci_dev points to 
+ *   Detects ICH2-M, ICH3-M and ICH4-M so far. The pci_dev points to 
  * the LPC bridge / PM module which contains all power-management 
  * functions. Returns the SPEEDSTEP_CHIPSET_-number for the detected
  * chipset, or zero on failure.