The change to reduce default smp_tsc_shift caused tsc shift to become

The change to reduce default smp_tsc_shift caused tsc shift to become
zero on slower machines, which make the fenced get_timecount methods
not used despite needed.  Remove the (shift > 0) condition when
selecting the get_timecount() implementation.

Rename smp_tsc_shift to tsc_shift, and apply it for the UP case too.
Allow shift to reach value of 31 instead of 30, as it was previously
(should be nop).

Reorganize the tc quality calculation to remove the conditionally
compiled block.  Rename test_smp_tsc() to test_tsc() and provide
separate versions for SMP and UP builds.  The check for virtialized
hardware is more natural to perform in the smp version of the
test_tsc(), since it is only done for smp case.

Noted and reviewed by:	bde (previous version)
MFC after:	12 days