cmd/ld: skip R_*_NONE relocations, fix Linux/386 build again

The last fix was wrong w.r.t C's operator precedence,
and it also failed to really skip the NONE relocation.

The offending R_386_NONE relocation is a absolute
relocation in section .eh_frame.

TBR=golang-dev
CC=golang-dev
https://golang.org/cl/6463058

src/cmd/ld/ldelf.c

@@ -658,8 +658,11 @@ ldelf(Biobuf *f, char *pkg, int64 len, char *pn)
 					p += 4;
 				}
 			}
-			if(info & 0xffffffff == 0) // R_*_NONE relocation
+			if((info & 0xffffffff) == 0) { // skip R_*_NONE relocation
+				j--;
+				n--;
 				continue;
+			}
 			if((info >> 32) == 0) { // absolute relocation, don't bother reading the null symbol
 				rp->sym = S;
 			} else {