Use the TSC delay(9) backend earlier on machines where we can. Also use

Use the TSC delay(9) backend earlier on machines where we can.  Also use
the TSC for delays even if there is a skew between the TSCs of the cores
as this doesn't matter for delay(9).

Gets rid of te unreasonable clock speed reports on Intel Tiget Lake CPUs
where the i8254 behaves in weird ways.

ok patrick@, deraadt@, mlarkin@