Split out handling of cpu family specific MSRs from cpu_init_msrs()

Split out handling of cpu family specific MSRs from cpu_init_msrs()
to a separate function that gets called after identifycpu() so that
we have the required information to handle the correct MSRs for each
cpu.

Additionally, move the handling of the DE_CFG_SERIALIZE_LFENCE and
IA32_DEBUG_INTERFACE_LOCK MSRs out of identifycpu() to the new
function so that they get set again after a suspend/resume cycle as
well, which in fixes TSC sync failures.

discussed with and input from deraadt@, mlarkin@