[CPUFREQ] X86_GX_SUSPMOD must depend on PCI

It seems commit 32ee8c3e accidentially
reverted cdc9cc1d, IOW, it reintroduced
the following compile error with CONFIG_PCI=n:

<--  snip  -->

...
  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  -->

This patch therefore re-adds the dependency of X86_GX_SUSPMOD on PCI.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Dave Jones <davej@redhat.com>