bus.h: rewrite comment describing intr_type

[mhorne]

Summary

Describe more clearly the purpose of these flags and where they are
used.

Remove grog's comment about revisiting the flags. At this point it does
not make sense to change this long-standing API, especially in light of
2cf7870864ea ("Collapse interrupt thread priorities").

Give a better example of a bus modifying these flags; I did not find any
existing instance where a bus changes the interrupt's type.

[markj]

sys/sys/bus.h

267

"will attempt to apply" sounds a bit strange to me, maybe "may apply"?

[imp]

I like mark's suggestion, but otherwise I think this is good. At first it was a bit of a squishy concept what this would mean, and in the end it's been used as an indirect way to give each of these interrupts a different priority level. We have some local hacks to adjust relative priorities based on the interrupt type relative to upstream as well, though I don't think that belongs here since it is a layer or two removed.

tl;dr: I think the new comments capture the state of things well and are a big improvement.

[mhorne]

sys/sys/bus.h

267

Sure thing.