[johnnym]

Update for IP28 and OpenBSD/sgi 7.3

Last week I could track down the problem source for IP28, which is actually two-fold: OpenBSD introduced the clockintr(9) subsystem between 7.2 and 7.3 and for some reason this didn't come without bad fallout for IP28, specifically the following commits break operation already during kernel boot:

• mips64, loongson, octeon: switch to clockintr (6b3715e (in sgi-never-retired-2 branch), f124c57 (in the official sources))
  
• kernel: stathz is always non-zero after cpu_initclocks() (8a1238c (in sgi-never-retired-2 branch), 9bcfcad (in the official sources))
  

I can workaround the first problem by deactivating clockintr for IP28 (see https://github.com/the-machine-hall/open...1510429607 for details) but this doesn't prevent the other breakage which produces the same result with or w/o the workaround applied. The workaround for the 7.2 issue with IP28 is not in the sgi-never-retired-2 branch but was applied when testing during the bisecting process.

The other systems I can test (Indy (IP22), Origin200 (IP27), Octane (IP30), O2 (IP32)) seem to be unaffected by the two commits mentioned above.