staging/rdma/hfi1: Disclose more information when i2c fails

Improve logging messages when there are i2c failures.
Clean i2c read error handling.

Reviewed-by: Easwar Hariharan <easwar.hariharan@intel.com>
Signed-off-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Jubin John <jubin.john@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>