Don't base the rate table selection based on the channel mode;
it needs to check whether there are rate entries in there or not.

PR:		kern/183428
Fix a typo introduced in r257338.
Remove references to an unused fasttrap probe hook, and remove the
corresponding x86 trap type. Userland DTrace probes are currently handled
by the other fasttrap hooks (dtrace_pid_probe_ptr and
dtrace_return_probe_ptr).

Discussed with:	rpaulo