dependency on CONFIG_CPU_FREQ

[Li Guanglei]

hi,

  I found runtime/time.c make SystemTap dependent on CONFIG_CPU_FREQ.
If the kernel doesn't turn on CONFIG_CPU_FREQ, it will cause the
insmod failure, e.g:

...
make -rR -f /usr/src/linux-2.6.17.1/scripts/Makefile.modpost
  scripts/mod/modpost -m -a -i /usr/src/linux-2.6.17.1/Module.symvers
-I /tmp/stap8uGyqO/Modules.symvers -o /tmp/stap8uGyqO/Modules.symvers
/tmp/stap8uGyqO/stap_11302.o
WARNING: ".cpufreq_register_notifier" [/tmp/stap8uGyqO/stap_11302.ko]
undefined!
WARNING: ".cpufreq_unregister_notifier"
[/tmp/stap8uGyqO/stap_11302.ko] undefined!
WARNING: ".cpufreq_get" [/tmp/stap8uGyqO/stap_11302.ko] undefined!
...

  I think most kernel running on servers/desktops don't have and
needn't CONFIG_CPU_FREQ turned on, at least it's true for RH shipped
kernel.

- Guanglei