6l, 8l: remove unused macro definition

        Their last use is removed in rev 70ed048caad2.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5532115

src/cmd/6l/asm.c

@@ -37,8 +37,6 @@
 #include	"../ld/macho.h"
 #include	"../ld/pe.h"
 
-#define	Dbufslop	100
-
 #define PADDR(a)	((uint32)(a) & ~0x80000000)
 
 char linuxdynld[] = "/lib64/ld-linux-x86-64.so.2";

src/cmd/8l/asm.c

@@ -37,8 +37,6 @@
 #include	"../ld/macho.h"
 #include	"../ld/pe.h"
 
-#define	Dbufslop	100
-
 char linuxdynld[] = "/lib/ld-linux.so.2";
 char freebsddynld[] = "/usr/libexec/ld-elf.so.1";
 char openbsddynld[] = "/usr/libexec/ld.so";