X86_GX_SUSPMOD must depend on PCI

This patch fixes the following compile error:

...
CC arch/i386/kernel/cpu/cpufreq/gx-suspmod.o
arch/i386/kernel/cpu/cpufreq/gx-suspmod.c: In function 'gx_detect_chipset':
arch/i386/kernel/cpu/cpufreq/gx-suspmod.c:193: error: implicit declaration of function 'pci_match_id' arch/i386/kernel/cpu/cpufreq/gx-suspmod.c:193: warning: comparison between pointer and integer make[3]: *** [arch/i386/kernel/cpu/cpufreq/gx-suspmod.o] Error 1

<-- snip -->

@@ -96,6 +96,7 @@
 
 config X86_GX_SUSPMOD
 	tristate "Cyrix MediaGX/NatSemi Geode Suspend Modulation"
+	depends on PCI
 	help
 	 This add the CPUFreq driver for NatSemi Geode processors which
 	 support suspend modulation.