debug/elf: SPARC64 relocation type is only 8 bits

debug/elf: SPARC64 relocation type is only 8 bits

https://docs.oracle.com/cd/E53394_01/html/E54813/chapter6-54839.html#OSLLGchapter6-24:

"For 64–bit SPARC Elf64_Rela structures, the r_info field is further
broken down into an 8–bit type identifier and a 24–bit type dependent
data field. For the existing relocation types, the data field is
zero. New relocation types, however, might make use of the data bits.

 #define ELF64_R_TYPE_ID(info)         (((Elf64_Xword)(info)<<56)>>56)
"

No test for this because the only test would be an invalid object file.

Change-Id: I5052ca3bfaf0759e920f9a24a16fd97543b24486
Reviewed-on: https://go-review.googlesource.com/33091
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>