makefs: Remove unused "mac68k" support

Obtained from:	OpenBSD 4f3c7809d4013a2eb3e75fc5e7bd2d8ae1f41843

usr.sbin/makefs/cd9660/cd9660_eltorito.c

@@ -110,14 +110,12 @@ cd9660_add_boot_disk(iso9660_disk *diskStructure, const char *boot_info)
 		new_image->system = ET_SYS_X86;
 	else if (strcmp(sysname, "powerpc") == 0)
 		new_image->system = ET_SYS_PPC;
-	else if (strcmp(sysname, "macppc") == 0 ||
-	         strcmp(sysname, "mac68k") == 0)
+	else if (strcmp(sysname, "macppc") == 0)
 		new_image->system = ET_SYS_MAC;
 	else if (strcmp(sysname, "efi") == 0)
 		new_image->system = ET_SYS_EFI;
 	else {
-		warnx("boot disk system must be "
-		      "i386, powerpc, macppc, mac68k, or efi");
+		warnx("boot disk system must be i386, powerpc, macppc, or efi");
 		free(temp);
 		free(new_image);
 		return 0;

usr.sbin/makefs/makefs.8

@@ -395,7 +395,6 @@ where
 is one of
 .Ql efi ,
 .Ql i386 ,
-.Ql mac68k ,
 .Ql macppc ,
 or
 .Ql powerpc .