Teach jedec_dimm(4) to be more forgiving of non-fatal errors.

It looks like some DIMMs claim to have a TSOD, but actually don't. Some
claim they weren't able to change the SPD page, but they did. Neither of
those should be fatal errors.

PR: 235944
Submitted by: Greg V <greg@unrelenting.technology>
Reported by: Greg V <greg@unrelenting.technology>
Reviewed by: cem
MFC after: 1 weeks
Sponsored by: Panasas
Differential Revision: https://reviews.freebsd.org/D19681