cpu/cop0/eret, recorded on firmware 6.61, has eret go to ErrorEPC and clear
only ERL with Status.ERL set, otherwise to EPC clearing EXL, with no delay
slot. Int_Eret already does that; the test joins tests_good.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>