Fix a bug where the callout might not be initialized before being used. 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.
Fix a bug where the callout might not be initialized before being used.
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

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