sched_4bsd: use the same switch flags as ULE

[mhorne]

Summary

ULE uses the more specific SWT_REMOTEPREEMPT and SWT_REMOTEWAKEIDLE
switch types, let's do that here as well. SWT_PREEMPT is somewhat
redundant when we also have the SW_PREEMPT flag.

This only has an effect for kernels built with SCHED_STATS.

[markj]

sys/kern/sched_4bsd.c

1554

This could be done before acquiring the lock, but it hardly matters.