More changes to MIPS may be required, as commented in D7692, but this revision aims to restore MIPS INTRNG functionality so we can move on with working interrupts. Reported by: yamori813@yahoo.co.jp Tested by: mizhka (on BCM), sgalabov (on Mediatek) Reviewed by: adrian, nwhitehorn (older version) Sponsored by: Smartcom - Bulgaria AD Differential Revision: https://reviews.freebsd.org/D7692