Rev 1.9 introduced another path where machclk_freq would be initialized
before the rest of setup was done (i.e. initializing the callout). Make
the one-time initialization a separate function and make init_machclk()
able to be called multiple times, any time. We depend on tsc_freq first
being updated from the highest priority eventhandler, thus we run last
and call init_machclk() to set machclk_freq. Also, don't initialize
static variables to 0.
Tested by: Eygene Ryabinkin
Approved by: re
441582040c