With preemption, the high FP registers may get enabled by cpu_switch()

before we grab the mutex. Don't assert that they must be disabled at
that point. We pretty much bypass all logic in that case anyway and
leave immediately, so there's no harm.

sys/ia64/ia64/highfp.c

@@ -92,8 +92,6 @@ ia64_highfp_enable(struct thread *td, struct trapframe *tf)
 	pcb = td->td_pcb;
 
 	mtx_lock_spin(&ia64_highfp_mtx);
-	KASSERT((tf->tf_special.psr & IA64_PSR_DFH) != 0,
-	    ("(tf->tf_special.psr & IA64_PSR_DFH) == 0"));
 	cpu = pcb->pcb_fpcpu;
 #ifdef SMP
 	if (cpu != NULL && cpu != pcpup) {