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/33091Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>

src/debug/elf/file.go

@@ -1021,7 +1021,7 @@ func (f *File) applyRelocationsSPARC64(dst []byte, rels []byte) error {
 	for b.Len() > 0 {
 		binary.Read(b, f.ByteOrder, &rela)
 		symNo := rela.Info >> 32
-		t := R_SPARC(rela.Info & 0xffff)
+		t := R_SPARC(rela.Info & 0xff)
 
 		if symNo == 0 || symNo > uint64(len(symbols)) {
 			continue