fix equality of eigen factorizations (#41132)
At least the newly added field `rcondv` may contain `undef` values, so
these can cause the same eigen factorizations not to compare equal. Not
100% sure whether the other fields should be ignored as well, but since
we didn't have them before, it seems at least consistent to ignore them
here.
fixes JuliaDiff/ChainRules.jl#422
